The GIF format is the only animated image format which is visible in any web browser, making it the de-facto format for basic animation on the web, despite terrible quality (256 colors), binary transparency (no partial transparency), and not so good compression.
Well, this may change. A few days ago, WebP reached support in most major browsers (Mozilla Firefox, Google Chrome, Microsoft Edge, Opera), when a 2-year old feature request for Mozilla Firefox got closed as “FIXED”. This will be available for Firefox 65.
Therefore, we surely hope web platforms will take this new format into consideration, and that everyone will stop creating GIF images now that there are actual alternatives in most browsers!