At my gym I made a body analysis which identified some muscle dysbalances. This was really helpful to create a workout plan.
There are also a lot of muscles I cannot train specifically when at home, because I do not have the right equipment at home. The trainers in the gym are also really helpful in teaching me how to get my body in a good shape.

On top of that I don't find it easy to establish the habit of doing workout at home. I prefer a change of location and also a dedicated time. My gym, which is located on my way back home from work really helps with keeping my schedule. I am doing this for 1.5 years now, two times a week and it works really great for me.

You see, everybody ia different and for some people like me a gym is a really nice thing. If a home workout is the right thing for you and you can also save money in the meantime, that's a great thing.