For all you know, windex may already be using Mastodon or some other service that's part of the Fediverse.
Your question should instead be aimed at the millions of people who still use Twitter, but of course you know the answer already: They use Twitter because millions of other people also use it, i.e. network effects.
Your question should instead be aimed at the millions of people who still use Twitter, but of course you know the answer already: They use Twitter because millions of other people also use it, i.e. network effects.