Simply because lovers are meant to laugh with each other, not at each other.
While the above is 100% true, there is still need to define the kind of laughter that is right and acceptable.
When we say relationships thrive on laughter, we refer to shared laughter and not the derisory type.
For the laughter and humour in your relationship to be considered suitable, it has to be shared. It has to be the type of humour that you both appreciate.
When your partner feels some type of way about a particular issue or matter, building your humour on those things, [and finding them funny alone] does not reflect on you as a good partner.
Here are the types of humour you need to totally avoid for the good of your relationship.
Have you ever poked fun at something and your partner didn't find it funny? That, right there is your cue to stop joking about it.
Many people do not enjoy having their family joked about. Regardless of their relationship with the person poking fun at them, they never take it lightly when their family or their family issue is the issue being laughed about.
If your humour is usually used in a way that exalts you and belittles your partner, you are doing it wrong.
You're preparing for a date and your partner asks “how do I look?” and your response goes, “you’re with me, you definitely look good!”
While this could draw laughter from them at first, if you keep repeating this kind of cocky humour, it won't be long before they start rolling their eyes in annoyance. [For more on cocky humour, google the name Zlatan Ibrahimovic.]
When you join other people in extensively teasing your partner, it may feel like fun to you, but it may make your partner feel weak, lonely and miserable.
If you must join friends in poking fun at your partner, make it light and be the first to note when he or she no longer finds it funny.
That way, you can catch fun and still have their back at the same time.