Married with kids here, i really love my wife but it's easier to say no to her than say no to my mother. I mean, moms are moms. If she took good care of your bf it is normal he feels obligated to make here happy/proud. It's just how it works.
Let's say i don't feel like going some place for X reasons, wife asks, i'll be naaaaah comon I don't feel like it. But, if my mom calls and ask for the same thing i might just go aaaah shit, ok then let's go. Another exemple, wife and I didnt want to make a big wedding party because we just think all the decorum around it is overrated. We were planning to go on vacation and come back married. But moms went noooooo we want to be there, you can't do this to us so we said aaaaw shit, let's do it here and invite friends and family so they can be happy and cry tears of joy... but really, we didnt feel like it.
Maybe it's not quite the same but i hope you can understand what i am trying to share with my personal experience. Those ''hinge events'' are important for all loving and caring parents and it's just normal to go out of your way to make them proud or just render them a service.
Just be happy he decided to go. You'll go with him won't you? You have what you wanted, his mom too, everybody happy.
Just dont jump to conclusion that he doesnt care about you. Maybe it's the case but with what you share i can totally relate to your bf.
Have a good one.