That’s a very good point. A lot of ordinary users think that if they’re syncing multiple devices via cloud they’re backed up. When one of their devices fails and they have immediate access to their files on the new device, it seems to confirm that to them.
We know that’s not true backup, but it almost always works, and it’s always worked for them. They’re not going to spend a lot of time or money for something they doubt they’ll ever need. But they can often be convinced to use Time Machine because it’s easy and cheap.