It's more efficient to have less demanding work carried out by less qualified people. I wouldn't have a problem with a dental therapist doing a check up either - they will refer on to/call in the dentist if they need assistance, surely.
When I go for an eye test, a technician does the technical bits and frees up time for the optometrist to do their bit. It's no different.
And it also makes sense for nurse and paramedic practitioners to see patients in primary care and do prescriptions for "easier" conditions. I think a lot of the time they are better - less cynical!