Part of the problem there is the fact they make it almost impossible to get upgraded!
There is also no sliding scale of down grading for groundcrew like aircrew have.
If they were able to grade people properly then perhaps more would be able to deploy.
The other thing stopping them deploying people is the duty of care stuff. If you choose to do active stuff whilst injured, it's up to you. If they deploy you injured, and you get worse (or injure someone else because of it) they get sued!
I'm sure there is a better way of dealing with injured people, but no doubt it's more difficult to administer than the one we have now...