This is one of the most common questions the FAQ gets, so it's worth a proper explanation instead of one line.
WebP was built to be small. GIF wasn't
TikTok's stickers use WebP specifically because it compresses animated content far more efficiently than GIF ever has. A sticker that's 150KB as WebP can easily become 1 to 2MB as GIF, sometimes more, for content that looks identical to the eye.
The 256 color limit forces extra work
GIF can only use 256 colors per frame. Converting a WebP sticker, which has no such limit, into GIF means every frame has to get its colors reduced down to fit that ceiling, through a process called dithering. Dithering itself doesn't inflate file size, but the color-limited encoding GIF uses overall is just far less efficient at storing animated content than WebP's newer compression methods.
Frame count adds up fast
A smooth, DM-length TikTok sticker might have 20 to 40 frames. GIF has to store meaningfully more data per frame than WebP does to represent the same motion, so the size difference compounds with every additional frame in the animation.
Is the tradeoff worth it
For sending in Discord, iMessage, WhatsApp, email, or Reddit, yes. Those platforms don't reliably support playing back animated WebP files, some browsers do, but chat apps mostly don't, so GIF is genuinely the only format that guarantees the sticker will actually animate wherever you send it. The bigger file size is the price of universal compatibility, and for a sticker still well under the size of a typical photo, it's a fair trade.