It might also have to do with how long someone tends to take. I tend to have a pretty slow metabolism and only need to defecate a couple times a week (to preempt any armchair diagnoses from people who think this is weirdly infrequent, every doctor I've had has always said this isn't a huge deal), so when I do, it tends to be in larger amounts. I've also found that it's better for me to take it slow and not strain as much, so sometimes I end up being on the toilet for more than just a couple minutes, which means that having something to do is nice.

That said, I do also have ADHD, so maybe people who are "longer and slower" toiler-sitters like me without ADHD might be fine without a distraction.

Not everything is ADHD.