The girl isn't permitted to have her bidaai yet because she didn't have a normal marriage and was left at the mandap, and the main guy, although he loves her and was more than happy to marry her acts like he married her out of compulsion and like he did some massive favour on her by marrying her to save her from humiliation, completely disregarding the fact that he was the one who got her in the mess by forcing her to marry someone she didn't love, and doesn't even once blame himself or realise she is suffering humiliation just because of him and then conveniently says that he won't permit her to enter his house and her new marital home because he doesn't have the permission of a member of the family who he thinks he disrespected by not asking their permission before marrying the girl.
So in this serial, forget suhaag raat, the girl is so ill-fated her husband won't allow her in his home until he has permission, without even questioning himself as to what will happen with his new wife if he is not granted permission for her entry.
Karthik is such a fickle-minded and immature man who is comparable to a radio consistently broadcasting only one station, that being tai. It's like he is ignorant to the world around him, intentionally turning a blind bat to anything if it involves him going against or speaking against tai. Honestly, since that incident before the 8 year leap where tai intentionally consumed poison after tai manipulated the evidence that karthik found that proved she was behind all the attacks on survi, he has become increasingly ignorant to tai's evil doings and in the most literal sense...lets her get away with murder!
The only shows where I have seen where the main guys do have a brain and a strong backbone are jamai raja and tashan-e-ishq, otherwise in every other show the main male leads are brainless, dim-witted and too slow to fend their wives or family from danger. Karthik's character is deteriorating, but thankfully at least now sonal is getting the chance to show her acting abilities with her character growing a much more stronger streak.