I'm not talking about people who genuinely forget names but rather those who, upon introduction, say "oh I'm terrible with names, I'll never remember yours". To me it's just rude and more or less saying you're not important enough to remember.
I don't mind if I meet someone and then see them a few weeks later and they've forgotten my name - that's not unusual at all, but AIBU to think those who immediately claim they can't remember names just can't be arsed?