A cold can't wait, it will go away in a week to 10 days usually, so they need treatment.
I was thinking about my kids visits to the doctor. 9 out of 10 times was because they were sick/running a fever and needed to be seen right away. A general check up and to get booster shots etc could wait for an appointment.
A woman I know has a Medi-Cal (Calif. Medicaid) type of insurance and she was having a problem with her feet. She had to wait almost 2 months to get a regular appointment. Oh, and she could only get one problem addressed. Complaining about something else required scheduling another appointment at a later date.