There are animal welfare laws on the books for neglect and cruelty.  In the warmer months groomers struggle to keep up with the demand and need.  

I agree most dogs can wait for a bath. However all dogs need basic care. Good grooming is healthy for the pet and those who live with them. Long nails are painful. Some nails curl and grow INTO the pad. Long nails force the foot in awkward position causing long term problems and deformities.
Pet grooming is frequently when bigger issues are discovered ie skin problem and new lumps which could be cancerous. We find things in heavy coats that have no. business being there like fish hooks!
Heavy winter coats are matted smelly and painful. Animal welfare laws have been written in every state. Neglect is against the law. Many owners CANNOT groom their own pet. Pets are difficult, some bite and or coats are too heavy already. Heavy coats can hide things like ringworm, which can be transmitted to people. Fleas and ticks are also a problem for both pets and people. Pets live in our homes. Everything they bring in could effect the owner and children.
Grooming is a basic care need that goes to the pets welfare.
Grooming is, in most shops  a low covid19 risk. We groom in back rooms, away from people. In most cases it is one groomer one dog. Before the shut down groomer were almost curbside already. They take the dog and the owner leaves. Groomers work one person one dog. Pet grooming is essential and low risk.