Community theatre is amazing for a lot of reasons. Almost everyone is volunteering their time, most people in a show aren't getting paid, and everyone loves what they're doing.
1. You get to know more people in your community.
By doing community theatre, I've met a ton of different people. Other students, teachers, fast food workers, stay-at-home moms, everyone. By having this, I've even met people who are going to the same college that I am in the fall and who will be in the same program as me. This makes my transition to college so much easier. Instead of going in and worrying about making friends so I'm not lonely right away, I'll have people I know I can go to for help.
2. You make lifelong friends, even if you're only in one show with them.
I haven't actually been in a show, I've been backstage for multiple for my community theatre. But I honestly trust and love the friends I've made, and I even know a couple people who are in New York. One of my friends will be in an Off-Broadway production, and another will be leaving very soon to stage manage a different Off-Broadway production in New York.
Honestly, I consider some of these people closer to me than most of the people I spent 12 years in school with. These people I spent a few weeks with. It was a few weeks, but that also means I spent hours almost every night for a few weeks with all of them. That build such awesome bonds comparable to no other.
3. You meet so many different people.
I've met people more liberal and progressive than me, but I've also met super conservative people while doing theatre. No matter what, they've all taught me something new. I've made friends with people I probably wouldn't have approached in any other situation if we're being honest.
4. You build your resume.
Not just your theatre resume, either. By doing theatre, you build your people skills, team working skills, and problem-solving skills. A production can't go on without working together as a team, on-stage and off. Also, if you're on-stage, you may have to improvise if someone forgets to do something (it happens to the best of us). Off-stage, a problem may arise and you have to figure out how to fix it before that scene comes up.
Using myself as an example, I recently did backstage for a show where we had to move a wall on- and off-stage. At one point, a part for one of the brakes fell off and I had to fix it while everyone was on-stage for a scene. I also had to finish it before the scene was over and we had to move it again. The pressure was real, but I did it and I consider that a quick-thinking, problem-solving skill.
You can also put it down as volunteering experience, which always looks good on resumes and applications. It shows you're willing to work hard and put everything you can into something that means a lot to you, even when you're not getting paid. It shows you want to do more than the bare minimum.
The moral of the story is if you love theatre but don't want to make a career out of it: do community theatre! Even if you are trying to make a career out of it, you should do it. There are no downsides if you really love it and are willing to put work into it.