Personally, I do not get dressed up and go running possibly far from my house, for such an invitation, though I will do so to go only to a smorg and chuppah, if I am not invited for the whole thing. But that is not the same as being invited for the “last” part of the simcha.
Someone whom I thought to be a close friend and who was a guest at my own simchas, sent me an invitation to their daughter’s chuppah, and then with an additional printed card enclosed for the simchas chosson v’kallah and dessert. So I would have had to go to the chuppah at 6 PM, then go home and come back several hours later at 9:30 or so. That was just not a polite thing to do. And they had the wedding at a fancy country club, so it was not about money.
I DO understand that not everyone, myself included, can always be invited to everything, finances and/or space could be limited, etc. for the baal simcha, but it is tacky IMO to invite someone only for dessert unless the simcha is VERY early. Exception is Sheva Brachos in a private home, where people often invite others just for dessert to help make the minyan, and just have immediate family for the meal.
I have heard that it seems to be customary nowadays to also invite many of the chosson and kallah’s friends only for dancing and dessert, but I don’t love this idea. It makes it seem like you are on the A list or B list of invitees, and that bothers me.