The counter theory for this is interesting.
Supposedly the reasons the Tepublicans are on board with this is because of anti-tax support. If you make it easy and cheap for people to file income taxes then they’ll become more complacent and accepting of more taxes. Making it onerous is to keep the frustration level up so people fight back against oppressive taxation.
If they really wanted to make it onerous, they'd stop withholding and make you write a check for the full amount owed every April 15th.
Too many people just see the 'refund' and never really realize how much in taxes they actually paid IMO.