The Republican health care plan as passed by the House (AHCA) will significantly reduce the subsidies going to help make insurance more affordable for middle and lower-middle income households. And it will, over 10 years, give a $765 billion tax cut to individuals making more than $200,000 or couples making more than $250,000.  This is one of several parts of the plan that favors the wealthy (and why this really is more of a tax-cut-for-the-wealthy plan than a health care plan).  

I'm not sure if many middle class families have yearly incomes of more than $250,000. If their income is less than that then they stand little to gain and possibly a lot to lose from this plan.