Makes sense maybe. I heard that Square Enix did try to get FFVII on Steam, but couldn't get through cert because they couldn't get it stable on Windows Vista or 7. VIII did have a PC version but I don't know if it fared any better than VII's.
Don't now why they don't just give the two games to GOG.
There really is no cert on Steam.
From what we've heard developers are left to their own ends to produce a product. If its broken then the developers are responsible for a patch, if Valve receives enough complaints they will pull the product and offer refunds.
Square already "fixed" FF7 for modern PCs and is selling it on their own online store, including cloud saving and always-online drm.
http://store.na.square-enix.com/store/sqenixus/en_US/pd/ThemeID.29853700/productID.250845500
...and securom