The draw of outlaw play is "control", pure and simple.
Most importantly the organizer can control who gets invited (and conversely who doesn't get to come back). This allows them to set the style and level of play.
We have a long-standing outlaw group of mostly pumpers and over time have been able to build up solid core of like-mined individuals that enjoy each other's company. Not to mention the cheaper cost (compared to BYOP fields).
When you play at a commercial field, you cede that control over to management and the refs. And there are numerous threads of how much douche-baggery exists on your standard walk-on day at the commercial fields.
Don't get me wrong, I have a paid membership at one of my local fields and hit it up probably once a month. But I do get tired of the many attitudes and hosefests there. So if it's an option, I prefer to play at our outlaw gatherings instead. And I know I can bring new/inexperienced players there for a proper introduction to safe, sportsmanlike, affordable paintball. I can't always say the same for the commercial fields...
It's like all things in life, you can't generalize. There are going to be some really well run commercial outfits that actively work to prevent overshooting and attitudes inherent in the sport, so kudos to them. And there will be some really unsafe outlaw groups that are one step above anarchy.
But at least with an outlaw field the members/organizer/owner can make the rules and not have to rely on anyone else for the quality of their experience.