The GOP is so hapless and weak that they can't even pass a repeal only bill.
The whole "Repeal and Replace" mantra during the campaign season was a dog chasing a car. The GOP never dreamed it would be in a position to do so which is exactly why nobody ever discussed what the replacement would look like. The dog finally catches the car...now what?
The simple fact is there is no way to do anything with healthcare that doesn't result in some demographic losing.
To make it cheaper for some, you have to make it more expensive for others.
Want to only repeal? Rates will come down for some, up for others and those with pre-existing conditions will be SOL because they either can't get coverage or the cost of coverage will be cost prohibitive.
There are no magic unicorns. There are no healthcare plans that allow all to keep their coverage and cost less. So what demographic are you willing to lose?
As soon as the GOP acts on healthcare in any way, they own it. And when their idea fails to solve the healthcare quandary, the ire of those affected will come down upon them and they know it. They don't want to own it.
Trump doesn't give a shit what's in any healthcare bill. He wants to say "I won" with no regard of what it was that he exactly won. A universal care bill written by Bernie Sanders could be put on his desk and he'd sign it. After all, he said that "we have to cover everyone"...those are his words. Any repeal or repeal and replace could be put on his desk and he'd sign it. He isn't worried about the fallout. It won't affect his life. What it will do is make the GOP responsible for what comes down the road.
The US was screwed when the healthcare industry in the US became a for-profit enterprise starting in the 60's. Prior to that it was largely non-profit. Research scientist gladly gave away their patents for breakthroughs like penicillin and polio vaccines. The profit motive bought a lot of advancement, lots of money into research but at a price. Costs skyrocketed and many being priced out of services long considered basic human needs.