I know for sure that if it were possible to sideload software onto my Switch or PS5, that would definitely benefit me as a consumer. The fact that I have a reasonably powerful computer attached to my TV but can't install software on it without convincing Sony to sell me a janky dev kit for way too much money is just wasteful.

Just about the only objection I can imagine is "piracy", but the locked-down nature of these platforms has surely not stopped piracy from occurring. Nor has piracy caused the failure of Valve's game store or the downfall of their gaming hardware.