Military boyfriend won't wear his uniform?

For our one year anniversary, I suggested to him that we do a professional couple's photo shoot. He was all for it, until I asked if for some of the photos he could wear his army uniform instead of regular clothes. I'm not a "tag chaser" and I don't want to show off his valor for selfish reasons, but it's an important part of our lives. He said he thinks it's tacky when milso's take pictures like that (in uniform). Obviously I won't push him to do something he doesn't want to and I'll respect his wishes. He's not ashamed to be in the army, so why would he refuse to wear his uniform for a few pics? Any help to deal with this? And any idea why he has this opinion? (This is him btw 💖)