Accounts have instance count quotas; you can get them raised, but it is a support ticket to do so.

And sometimes, that is hard. I've had Azure support not able to understand what quota they need to raise / what quota is being requested. I had to at least link them to their own documentation on it… (partly the confusion is that quota support tickets allow selecting the quota as a piece of metadata on the ticket, but only for some quotas, and of course, mine was for one of the ones not listed. Why they don't just list all of them is anyone's guess.)