A dragonborn doesn't seem to have lips for kissing, for example. How does that impact the character? Let's say I want my character to romance Shadowheart. How strange is it going to look watching the two of them together? Just feels kind of creepy to me.
Dragonborn do have lips. You can see them articulating every so often, and when we see a Dragonborn NPC their lips will probably move as they speak. Snouts don't necessarily mean a lack of lips. Giraffes are a good example.
Also, a Dragonborn is an intelligent creature. Just because they don't necessarily kiss to show affection (As I recall, they do a sort of jawline nuzzle instead according to a novelist) doesn't mean they can't understand the meaning behind the act and understand what a kiss means to their partner.
So a Dragonborn sharing a kiss with a more human-faced partner can make complete sense. It's not how they'd show affection to another Dragonborn, but they know the purpose of the act and enjoy the affection meant through it all the same.