GF loves kissing but not during sex

My gf and I (both 21) are very intimate and kiss all the time. But any time she’s getting stimulated down there (penetration or otherwise) she seems much more reluctant to kiss me, or at least doesn’t actively want to. Like if I kiss her during she’ll kiss me back for a bit but then stop and won’t re-initiate it. She’s very eager to before it and immediately after she finishes, but during she seems to prefer not to. This is the opposite of what I’ve experienced in previous relationships, so I was wondering if anyone else has experienced this or can explain why.