You get a smoother ride with a nicely waxed board. Smoother turn initiation, better acceleration out of turns, more consistent glide, etc. I definitely notice when my board needs a wax or has just had one.
The problem with never waxing is that the base abrasion builds up to the point where waxing just won't make it better, you'll need a base grind.
To each their own, but I don't like spending hundred$ on a board only to have less than optimal performance. Kinda like buying your dream car and never changing the oil.