I guess it also depends on culture. In Latinamerica many people consider birthdays a big deal so forgetting it would be considered a faux pas.

For me personally I care if my partner and close friends remember, coworkers, my dentist, etc. I don’t give a damn but if they so happen to congratulate me or send a gift or whatever, I thank them graciously and try to correspond in the same manner when it is theirs.

For example, my yoga teacher found out about my birthday because SO sent me flowers to the studio so I could enjoy myself starting the day, so said teacher gifted me a box of my favorite incense. It was a nice touch but definitely due to circumnstances. I enjoyed it nevertheless. So now I will be getting her a nice beautiful plant for her balcony.