The underlying cause of this whole issue is the changes in tax policy instated in the Tax Reform Act of 1986, previously income was taxed at higher rates unless deductions were utilized which forced those earnings back into the economy creating jobs funding research, etc.
But isn't that just a reflection (and after-effect) of a more fundamental, underlying cause -- that is, the extent to which low- (and medium-) skill labor itself has become devalued, in recent decades -- along with, of course, the very class of persons taking those jobs? Along with a host of other changes in attitudes (sharply) favoring the welfare of the high-skilled -- and above all, of the rentiers -- over the welfare of those who actually do the bulk of the work that keeps our civilization actually running?
Which is presumably what motivated the actual votes on the particular pieces of legislation you (quite validly) cite.