Well, you are the one who thinks their wedding is such an amazing event that people will be so excited to give up an evening with their partner to assist, not me! In real life, they won't but people are polite and will pretend to be super enthusiastic whilst frantically trying to find an excuse, or will attend because they feel they have to.
Wow Doncorleone. Do you not have many friends ?
I'm not surprised if you really think like this.
IME, people like being invited to spend time with friends, at parties. Of course, if they don't wish to, they are completely welcome to decline the invitation, but what kind of people do you mix with that you think 'going to a party' = 'giving up an evening with their partner to assist' ? 
If I receive an invitation to help celebrate someone's 'life event', my usual response is to think "How nice" - firstly, how nice that they are celebrating their wedding / birthday / anniversary / whatever, and then 'how nice' that they've been kind enough to invite me.
As for this ridiculous comment :
I understand your wedding is for show, it looks good to have as many guests as possible to tag you on social media
Words fail me. You must have a pretty sad and bitter life if you can project all of that tosh from a bride to be checking that it is OK to not invite colleagues partners to her wedding 
LoksBetterWithaFilter I hear you. I've been to a wedding where I was an evening guest, and got a phone call the day before the wedding asking if I'd like to come to the meal as someone had had to drop out last minute. Like your parents, I thought 'oh, how nice of them to ask me' and didn't strop and ''cut my nose off to spite my face' and refuse to go because I'd originally been invited as an evening guest. Rather like your parents, I live in a normal world where I have grasped that being a colleague of someone, or happening to sing in the same choir as them, or play a sport alongsdie them means I am not as close to the couple as their lifelong friend they went through school with, or their cousin, or sibling. It isn't too difficult for most people to understand.