For starters, they don't really exist on the east coast north of the Mason Dixon line. So there is not much to talk about for a good amount of people who hang around here. Same applies to the Rockies. Once you leave the midwest and the south there isn't much until Arizona/Ca.
Second, a lot are smaller schools with heavy religious identities. Baptist schools, methodist, christian etc. Not for everybody
Third and most importantly. They have weak academic profiles. You're going to have a very hard time finding a HA NAIA, odds are there are better academic opportunities closer to home.
Top NAIAs are good, better than the bottom D1s. But the lower half of NAIA baseball will resemble a HS game more than it will a D1 game. This is what a former NAIA coach told me on a recruiting visit at his new D1