For me GMRS was a good entry point into radio. As many have said, there's no test, family is covered and if you have Repeaters in your area you can access you can have pretty good range for communications.
A lot of us move from GMRS to HAM because we want/need more options. There are way more 2M/70cm Repeaters in my area I can use. With my current Technician Class License I can cover a Very Large area on the limited amount of 10M I'm permitted to use and once I get my General Class License I'll have even more HF to play on.
For many GMRS is the "Gateway Drug" into radio and for others it's as far as they go. It all depends on your needs/wants.
Personally, I really love HF so HAM is where it's at for me but I also have my GMRS so if my family needs to use a radio that works better than the little FRS radios they're covered under my license.