A big part of capital's success is selling the idea that the interests of the relatively well-off working class i.e. home-owners, decent wage, established careers, good pension, and a little bit of savings - and of those who aspire to that - are more aligned with the interests of capitalists than with those of poorer working class people. Of course, under capitalism they might be e.g. low taxation, low benefits, markets stable, controlled inflation etc., etc.
But the elephant in the room is that we don't need to live under capitalism - it's not an inevitable permanent state of affairs.
But one of the left's failings* is that the idea of a radical shift seems so far away that many in the w/c would rather take their chances on getting the best from the status quo.
*It accepted the logic of neoliberalism and pivoted away from a broad based economic movements of, by, and for workers, to atomised identarian causes (essentially radical liberalism) led by middle-class careerists.