Some of the benefits of riding a group that is well disciplined is the gain you get in speed for output due to the rest time you get not pulling, learning to maintain a proper speed while pulling, and the safety of riding with such a (properly taught) group at speed/close.
It really burns my ass when you get out to a "no drop" group ride with some low (or high as perspective may have it) advertized average speed, and then it turns into a hammer-fest and leaves new riders to that group off in the weeds somewhere to catch up at some regroup point by themselves. The whole point of making a group ride IS to ride with others. Even if you have a rider who gets shelled, there should be some person sweeping the group and making sure these folks get back safely. Heck, folks can ride alone from home.