They work for recruitment because... they're cool.

Sure, but the purpose is recruitment. They wouldn't do them if they didn't get anything out of them, and what they get out of them is PR and boosts to recruitment efforts.

Why do small regional non military equivalents exist then?

People fly air shows with crop dusters.

I mean, also statistically, it is bound to inspire young people who potentially might be interested in picking an aviation related future. Maybe they will invent something they otherwise wouldn't have.