Seriously, why haven't the Steam, GOG nor Fallout Anthology releases of Fallout 3 been updated and tweaked to be optimized for Windows 7 and above, while Fallout 1, 2, and Tactics don't have that problem at all, despite being way older games? AFAIK, there is not official patch to optimize it for Windows 7 and later. Why is this?

Because there is no need besides installing DirectX 9. It is not a problem with the OS in themselves (aside from DX). Now there are problems with newer computers and the games but fixes for that should be baked in already.

Few developers release compatibility patches. They do redux or enhanced editions instead and sell those.