Not because a private organization said so. Because a very large body of academic institutions got together and agreed that it should be so.
Easy to blame the NCAA when you don't like what the nation's colleges and universities have agreed upon in sports. But one should never forget that the NCAA can't make broad, far-reaching decisions without the support and agreement of at least a majority of its member institutions.
Want to change the rules? Have at it. All you have to do is convince a majority of colleges and universities to raise their hand. Or maybe all it would take would be the majority of the 128 institutions in FCS, or maybe even just the majority of those in the Power 5 conferences.
We made college athletes amateur, and defined that as not being allowed to receive pay to play. We did, our society. Don't lay that one on the NCAA as an institution, it's a cop-out.
We did that when there wasn't major revenue involved, when we knew less about the potential destructive results to the human, before we had such popular and well compensated professional ranks. Status quo doesn't make things right. Large institutional control doesn't insure fairness.
This country was borne out of demanding change when the system in place no longer served this country and was patently unfair. These major academic institutions began as educational institutions and many grew into athletic factories when the revenue encouraged it and the rules allowed it. I'm sure the cotton farmers weren't excited about losing the free labor either - might have gone to war over it.
So, I lay this on the feet on the NCAA for not evolving with the times and hording the money that has developed. Then, I blame those that enable them.