Previously, I had kept my Twitter account to cross-post from Mastodon.
I reasoned that cross-posting to Twitter would encourage others to migrate to the Fediverse.
That probably didn't happen because no one saw my tweets anyway.
But the clincher -- the thing that made me realize that Twitter was just a big waste of time, energy, and bandwidth -- was the realization that my posts are already being cross-posted to Twitter anyway by other people.
Now that I see this, I'm done.