VBProject: All because multibillion Valve is too lazy and too greedy to develop a legacy game downloader for 98/XP/7 users and keeps using Chromium for everything.
No GOG - no buy.
As for the first quoted statement: more likely the reason is that Valve doesn't want to get sued for many millions of dollars for facilitating the use of unsecured OS'es, which is exactly what would happen if they did what that statement is asking for.
As for the second statement:
as if GOG is going support Windows 7 forever. I'm sure it won't. And even if it did, that would still be a moot point, because pretty soon hardware manufacturers are going to stop supporting Windows 7 too, therefore users won't be able to use it forever for that reason either, as eventually their old hardware will breakdown and need to be upgraded to new hardware which won't work with Windows 7.
Bottom line is that there is no possible way for users to cling to Windows 7 forever, unless they are going to endlessly re-buy old & used hardware for the rest of their lives every time one of their old machines breaks down. And even then, users are not going to be able to play new games on those machines, so they are going to be mostly useless for that reason, other than for the niche purpose of playing ancient games only.