In the past, concessions would be given to workers to stave off talk of revolution. Think of the new deal, etc.
These days, whether through incompetence or ideological intent (the end result is the same so the distinction doesn’t matter much to me), the ruling class just will not allow any pumping of the brakes, any tiny release valve to stop the pressure building.
I find it a fascinating phenomenon that they are incapable of doing something positive for society, even to save their own skin. It baffles me, especially considering how successful it has been in the past.
I think it comes down to basic petty politics. Manchin and Sinema don't want $15 but also don't want to be seen voting against it and Biden doesn't care enough about it to delay the stimulus bill that he thinks is more popular and more important.