Why do you need another cam, may I ask ?
lots of reasons;
1. you have a closed CAM where you can't change any of the speed/material settings. perhaps you're in the market for something novel, new, or that some other system supports but your own system doesn't. example: Grandio by Voco. or Crystal Ultra. you ask your CAm people if they know anything about milling these materials and you don't get a straight answer, or a flat rejection. at this point you'll be looking at CAM options that can do what you seek, if the system is locked.
2. licensing fees too high.
3. poor CAM customer support.
4. poor performance. you'll notice it takes a consistent 3 hour window to cut your denture base, so you go after new CAM that can do it quicker - new CAM may not be entirely necessary but if your support doesnt want to help write new strategies, or give you better ones, then its time.
5. dislike for the locked options. your system need not be fully locked, but it may be locked for the Denture purpose for example. in AG machines all you can do with denture manufacturing is the Baltic system, so if you want to mill the Ivoclar way, you'll need to get new CAM.
that sort of thing.