@Lee_in_Iowa It depends on which server you are on and other factors, but rate-limiting is generally done (not just on Mastodon, but on Internet protocols in general) to prevent denial-of-service attacks.
Doesn't mean you were doing anything wrong, by the way. It's just that if there were no limit, someone with a script could bring down servers by simply flooding them with bogus requests.
It's possible you might want to talk with your server admin about whether they have this set too low.