Because they're a bunch of sellout Establishment cowards who would rather kick the can down the road for a few years than deal with this problem courageously and thoroughly?
Just a guess...
In any event, Donald Trump does not think in such terms. He only thinks "big league", and whatever bill he ends up signing will be "great", comprehensive, and have his stamp on it so that he can take credit when it succeeds.
There's no way that this President is going to sign some half-assed non-solution that will not at least try to solve the problem. Such a law wouldn't help him politically, and wouldn't help the working class people who voted him into office. Therefore, that's not what will happen...
You do know that he endorsed universal healthcare, don’t you? “The government will pay for it.”