This is probably a dumb question, but why is this a rule? Would games just turn into wrestling matches under the basket every possession? As people have pointed out, it's rarely called right now and it usually doesn't have a lot of impact on the game, so I'm wondering if it really matters.
I mostly ask because, in general, I think that sports are better and more fun to watch when there are fewer rules that officials have to enforce.
Looks like the rule was first created in 1936. I'm sure before the three point line, it was necessary to have it to prevent exactly what you described. But now with the line there's naturally better spacing and movement.
Although I wouldn't underrate its impact now. If it wasn't a rule, I imagine more teams would design their entire offense around a dominant big man just staying at the basket. Even though it might be rarely called now, I think the rule still affects how most teams design their offenses.