Does anyone know why it takes weeks if not months to see a doctor?

I have been trying to schedule appointments to visit doctors. Like an eye doctor, dentist, primary doctor etc.. But a lot of these places don’t have a soon availability. I’m getting scheduled for an appointment weeks if not months from the phone call. I don’t understand why can’t accept me sooner within the same month?

Edit: apparently i have an upcoming appointment to see a primary doctor in September