In addition to having multiple forms of cardio available (rowing machines, stationary bikes, treadmills, ellipticals), gyms have a ton (ha) of specialized strength-training equipment that makes life a whole lot easier if you intend to take physical training seriously. Although it's better than nothing, merely having a weight bench or set of dumbbells at home (or, god help you, a Bowflex) is going to be inadequate for making steady progress on compound lifts that target large areas of your body and develop functional strength; a decent gym will have a squat rack/power cage, free weight section with padded floors for dropping weights (sometimes completely necessary), benches, and a few assorted machines, at the very least.
Exercising at home can be fine and good, but you run the risk of hurting yourself pretty seriously if you do it wrong enough. Even if you don't want to plunk down the money to have a PT (who may or may not actually be good at their job) show you proper form for lifting and whatnot, if someone else at the gym sees you doing an exercise with hazardously poor form (i.e. rounding your back during deadlifts, hnnnnnnnggggghhh), someone is likely to at least tell you to stop before you hurt yourself, if not take the time to show you how to do it properly, whereas if you're doing it wrong at home, odds are that your poor technique is going to land you in the chiropractor's office or emergency room.
It's not very attractive to the shy and/or awkward, I know, so if you can't work out while anybody's looking, you're gonna have to step outside your zone of comfort the hard way. I used to do all of my running at night because I didn't want people looking at me when I was sweating my ass off and breathing hard, but after doing it for long enough I realized that I had absolutely no reason to give a fuck about who happens to drive past, and will do my thing without any irrational fear of judgment; same principle, if the gym intimidates you, you're gonna have to attend and have nothing go wrong long enough for you realize that your fear of it is irrational. It's not a highschool locker room, so even if you catch a shitty vibe from someone, it's not like they're gonna walk over and fuck with you, just ignore them and do what you showed up to do in spite of them because they're dicks that are there for the wrong reasons.
I'll tell you this, OP: it sure as hell isn't a waste of time.