Yes working out on your own can be effective, but there are days when you need that extra push. When you find a great gym, you want to go to see your "family." It makes the days you don't feel like going a little easier, because you know that you have people their who will notice when you're gone. Also they can help push you to do more reps or weight during your workout. There's so many benefits, but these are just a couple.

Go out there, find a gym that fits you, and get after it!