Mental inertia. It's the same kind of thinking that keeps some people using Windows. They've convinced themselves that the option with the familiar name will take less effort to learn than the one with the new name, when in fact the mental effort required to make the familiar-named thing work properly is greater.
Okay, it's more like the people who all refused to leave Xitter until recently. It took something very like the original Twitter (Bluesky) for them to finally get the mental gumption to make the switch. Prior to that, mental inertia kept them in place.