Guy's Behavior

Why didn't he wish me happy birthday?

I know it may not be a big deal to some people but I've had a friends with benefits for 2 years and lately we've gotten more close and affectionate towards one another. His birthday was a couple weeks ago and I wished him a happy birthday. My birthday was yesterday and he didn't wish me a happy birthday and I know he knew it was my birthday! His whole family (mom, dad and brothers) all wished me a happy birthday even. I know he's only a friends with benefits but I'm so hurt and upset about this. Why do you think he never wished me a happy birthday? He couldn't have been that busy to send a quick message to me. He was active on fb a lot as well.
Why didn't he wish me happy birthday?
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