Gym

It's more about health than looks or building muscles (which is also fine if you want that). Most office workers have a sedentary lifestyle without much movement. This is one of the risk factors for type II diabetes in the long run, also cardio-vascular problems and other issues. A human body is supposed to move frequently, either through cardio or resistance training or else. It doesn't have to be the gym, can be another sport or hobby like swimming, cycling, walking, or something like that.

I am addicted and obsessive compulsive about working out and feel like a fat POS if I don't go every day. I'll run at 8am still a little drunk from the night before. I don't think I have taken a week off from working out in almost a decade, and I have had visible abs the entire time as well. Just becomes routine. 

I used to be obsessive about going to the gym because I was scrawny and didn't like the way I look. Now that I've been at a good weight for a while, I've moved away from only heavy lifting and do more functional training now just to be healthy and feel good. I usually only workout 3 times a week though. 

Gym is all about health and physique. I've worked out consistently for 20 years, even in those times when my diet was so bad that I put on 50 or 60 lbs. As a result, I'm almost never sick and I have very strong bones and have been able to withstand a lot of very hard falls with no injury (I used to be a skater and have fallen countless times very hard and no broken bones). Fat loss is principally about the kitchen. My diet is an abomination which is why people are always shocked that I work out 3-5 times a week. They look at me and are like, "Hoooow?" Well, yeah, but I've hardly been sick in 15 years. 

One day your “fit body” will deteriorate. Or just as likely, your body is not as fit as you think it is. Most of the people are not obese in the gym, just an fyi. Stand outside one and watch the people who walk in n out. 

I'm guessing you are in your teens or early 20s.  I didn't need to go to the gym then, either, and ate and drank whatever I wanted and it didn't make a difference.  Give it 5-10 years and you'll have a different experience.

More to the point, there are a lot of other benefits.  I get an endorphin rush from going, and just moving and sweating feels good.  Exercise is basically the one miracle drug we've found; it has a TON of physical and mental benefits if you keep with it, whether that's reduction of cardiovascular disease to reducing the chances of dementia.  Going to the gym helps me sleep at night.  It's good place to socialize and make new friends or meet potential romantic partners, which is a harder and harder thing to do as you get older.

And yes, it can help you look good and make you feel more confident as a result.

I hit the gym to look hot. Don't care about anything else 

Hinge and some matches will suffice