Yes but if Steam shut down you’d have no way to get to the installers again and you’d be left crossing your fingers the machine you installed them on doesn’t die.
I don't see too much of a difference other than Steam has more proven longevity - even if the developers that sold games on Steam don't. I can still download Dungeons of Dreadmor from Steam even though the company appears to have disappeared in 2016.
Think it through. Of cause you cant get the games files if the provider goes offline. You can make a backup of any of your games in steam, which will make it possible to install it again offline on other machines.
Hacks already exist to make the games not check the servers, and only stop working after new Steam updates. If Steam were to never update again it seems likely the hacked dlls would work forever.
I don't see too much of a difference other than Steam has more proven longevity - even if the developers that sold games on Steam don't. I can still download Dungeons of Dreadmor from Steam even though the company appears to have disappeared in 2016.