Steam is competent at what it does and has been for decades. No other online game store is as good as what it does: Nintendo, Epic, Microsoft, & Sony have all failed to do well what Steam has gotten better at over the course of 2+ decades.

People would likely juggle the use of two stores if the value proposition was great enough. But it isn't, which is why Steam dominates and all their competitors operate in comparatively tiny fiefdoms.

Steam has problems but it also has a vast feature set. The family sharing and refund policy are both seriously great, for example. Personal calendar is also really, really cool (and bad for my wallet).