Standard terms on bills are 30 days. Perfectly reasonably to expect that.
Some didn’t receive an email for whatever reason, some while on vaca due to the short lead time, etc.
It’s perfectly reasonable to expect to be notified 30 days in advance of a bill being due, like just about any other bill you get.
As for the “you should just remember it”: Why? With about 38,172 things to remember, should we all duplicate what goes on in the computer systems of every entity with which we interact? No, that is absurd. It’s a standard operating procedure (yes, I know, there are exceptions) to be notified 30 days in advance of a bill being due by the biller.
That’s why people whine. Perfectly reasonable, doesn’t mean they are guaranteed to get their way, it just means some have a reasonable complaint.