That’s probably the emergency animal hospital. Sees the pet same day 24/7, pet waits with you in parking lot until they’re ready, and is taken immediately back to you when they’re done. Prices are high, and non-emergency services aren’t available. For instance vaccines/microchipping.

I do not know why such places don’t offer standard services. The one by my house was nearly always empty, but still would not give my dog vaccines.