@FlexpertHamilton and
@SW15
I was going to add, a lot of boxing gyms you will see are honestly geared towards fitness classes for the average person that wants to get into shape and have fun doing it. Most people honestly get bored rather quickly with standard workout routines (lifting, cardio, etc.), so something like a boxing class is the right fit for them. It's fun and active, you get to hit things and try out different techniques, etc.
I personally would not get into boxing or MMA with the intent of actually trying to compete. I just cannot think of any real reason to do something that will very likely cause injury or brain damage for no real benefit. I knew a guy many years ago that was obsessed with MMA but honestly had no real athletic talent. Anyway, he signed up for some sort of amateur fight and spent many months training and preparing for it. At some point during the fight he ended up having his arm broken and that was it lol. This guy spent a ridiculous amount of time and energy invested into something that would have brought no real benefit to him, and to top it off he ended up getting a serious injury from it. Most of the guys I've met that get into this crap typically aren't very bright and don't have much going for them. Any guy who has a career or livelihood would not get involved with something like this.
If self defense was a concern, just buy a damn firearm lol. Being trained in BJJ or boxing is not really going to be much help when you have 4 guys that cornered you in a parking lot.