I don’t know what a .webp file is but I don’t like it. They’re like a filthy prank version of the image/gif you’re looking for. They make you jump through all these hoops to find the original versions of the files that you can actually do anything with.
Gimp, who’s developmental team consists of a bunch of volunteers supports it, the reasons those companies don’t support is is either because they don’t care about users (Adobe), or because they are pushing their own, proprietary format. (Apple) Microsoft directly competes with Google in the cloud ecosystem space and therefore wants to make using Google as painful as possible. (See microsoft making it a huge pain to switch the default browser to chrome)