Uhm... yes. Most people use them.
You can make better gear than drops/mission rewards (make greens, reverse engineer until you get the blue schematic you want, build that). And you can make gear for your alts. For instance, my agent is churning out heavy armor for my trooper.
You can also make a ton of money selling (blue and better) gear on the GTN.
You generally would want skills that work together (armormech, scavenging, and underworld trading).