My dad forgot my 30th birthday last year. No text, no card, no gift. I was beyond hurt. My mum who is separated from him eventually emailed him 2 days later after which he text me twice asking to call me and when I didn't answer him he left it until Christmas (2 weeks later) as he knew I was going to a family function and he brought my birthday/Christmas gift.
We didn't have a great relationship before but I always made an effort for his birthday. His excuse was he was busy with work.
So yeah, basically I'm hurt and I will be hurt for a long time. It takes 2 seconds to send a happy birthday text, I will always send them to people and tbh the texts/messages/cards mean more to me than anything else (even better if you can spend some time with me, but not required as people are busy!)