My boyfriend doesn't want to go with me....

So I just turned 18 my boyfriend is 20 I'm still a senior in high school and he is on his second year of college.. so I asked him to go to my homecoming (mind you we've been together for almost 8 months!!) and he doesn't want to go he won't give me much of a reason or anything it kept saying it would be weird which I understand he is older but people bring 20 year olds all the time and people from other schools and things  nd I'm just disappointed because I don't even get to go with my own boyfriend so my question is how important is this really? Should I just be letting it go? Or is there something I can do to talk him into it?