Yeah, I know it doesn't matter. But I guess it matters to him.
I think why it really matters is because he didn't want Jesse trying to interfere with our relationship and have Jesse create a bunch of drama, which neither me nor Bobby needs. But...
Bobby said himself that he wanted to keep it a secret from Jesse (and only Jesse, for the record. Anyone else could know.) for a few days. It had been a week since we had been dating, so I didn't figure it would have been that big of a deal. That, and it couldn't be kept a secret from him forever.