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.
Edit: honestly I assumed it had something to do with Google protecting themselves from image piracy shit
Everytime a post gets displayed on a screen, it got transferred over a dozen routers, parsed by a network card, decoded byte by byte to get each pixel's color and then displayed on screen
Transferring and decoding all that extra data on millions of computers isn't free
When you make an instagram post that gets seen by millions of people it's absolutely not negligible to use webp vs a jpg and choosing one over the other because you're just... used to the extension? is downright getting unacceptable if you are at least a lil tech savvy
People need to start using newer file format for real now. It's been 20 years