Is the reason for few established house churches a lack of leaders or something else? What a question. There are definitely different reasons for a lack of house churches, but I want to point out one that is, in my opinion, so obvious that it usually goes unnoticed.

Ease and comfort.

Amos 6:1 starts, "Woe to those who are at ease in Zion..."

I can summarize by saying that around 90% or more of employees wouldn't show up at work if they didn't have to put in any hours to be paid (ie. they were paid whether or not they came to work) and that in the same way, christians usually won't work or labor or fellowship the way the Bible shows or follow God's leading because they don't have to in order to be 'saved'. But I'll continue:

Sir Isaac Newton was an English mathematician and was considered to also be a believer by the Protestants of his day. His First Law of Motion states that "a body at rest will remain at rest unless an outside force acts on it, and a body in motion at a constant velocity will remain in motion in a straight line unless acted upon by an outside force."

I think in Newton's first law of motion, he unintentionally captures and encapsulates so many relevant truths about life and godliness or about the natural order and the churches.

A person who lives in relative ease and comfort (ie. a body at rest) about 99% of the time will not step outside his bounds of ease. But a person who lives more of an active lifestyle (ie. a body in motion) is more inclined to step outside his comfort zone and act because he's already 'in the motion' of acting. This is why Jesus didn't tell His apostles to pray for Him to send ministers and pastors into the harvest field but told them to ask Him to send laborers. Anyone can be a laborer (you don't need to be a minister and don't need a title or position): a laborer is valuable to God [ahead of 'a minister'] because a laborer is someone who labors until the needed task is completed. This was why Jesus chose the twelve men He chose for service; they weren't ministers or unique (in fact, they were rather rough-hewn and unpolished sinners); but God knew and Jesus saw that these men were laborers who would see whatever mission they were given through to the end. Sure enough, as a laborer, Paul could later tell the Galatians, "My little children for whom I labor in birth again until Christ is formed in you" (Gal. 4:19). 

In spite of Jesus's command to the apostles to go first to the Jews and then the Gentiles, the apostles would not do it. They remained 'at rest' in the comfort zone of being among the Jews until acted on by an outside force (ie. persecution, starting with Stephen); then they were 'forced' to take the gospel to the Gentiles. The Church then remained 'in motion' until acted on by another outside force (ie. the formal acceptance of christianity by the state into an institution and 'church buildings' which caused the churches to cease 'motion' (ie. Life) and to return back to 'rest' (ie. death)).

Like the human body, the Church can only retain Life or relevance as long as it is in motion. The central nervous system makes sure the body remains 'in motion' even while physically at rest because everything God created (observed well in atoms, neutrons, electrons, etc.) maintains life or literally continues to exist only in continual 'movement' or 'in motion' (as Paul stated, "In Him we live and move and have our being/existence" -Acts 17:28) as God Himself is 'alive' in the way of being constantly 'in motion'. (Heb. 4:12.) Therefore, one of the overlooked but foundational reasons there are few house churches is because most christians enjoy a level of comfort and ease that automatically makes them passive, lazy, lethargic, unmotivated, 'spiritually depressed' or 'dead', indifferent, self-centered/self-serving, and apathetic. 

The charismatics are waiting for God to bring revival; the fundamentalists are waiting for Jesus to rapture them; everyone [else] is waiting for someone else to take charge and take initiative (this is one reason people value pastors and the clergy)-- similar to 'Genovese Syndrome' aka the 'Bystander Effect'-- but as usual, God is actually and really the one who is waiting for [groups of] people to gather and approach Him 'in the prescribed manner' so He can 'pour out His Spirit' and blessings again. 

Jesus wanted the apostles to go to the Gentiles long before they actually and finally did. In the same way, there are many good things God wills to be happening right now that will have to wait because of the inactivity of His people. "A body at rest stays at rest." Most of God's works on earth hinge on the obedience of God's people, not on 'God's timing' as is often the commonly-held view. This is true from the NT backward all the way back through the Old Testament (eg. even under the Old Covenant and the Law, the Jews were told to include the Gentiles; but from that time even up into the times of the New Covenant, the Jews refused to do so; therefore, God's work was delayed). 

There is little faith, courage, vision, and motivation/power among christians right now, so the greater portion of what God wills to do right now will have to wait to begin after tremendous hardships (ie. economic collapse, civil unrest, war with other nations, and natural disasters) and personal hardship (ie. open or sponsored persecution of believers) break on the churches and the world. That's going to be a while coming. When it does happen, then just like was always the case with Israel in the Old Testament and was also the case in the early Church, the churches will then begin to 'tighten up' because hardship and persecution are upon it. Then, as alluded to in Malachi 3:13-18, there will be a major line of demarcation that will manifest as some christians will abandon the faith and run for their lives while others will decide to repent, turn back (return) to God, and do things His way including the pattern and practice of fellowship, house church, and 'church'.