Simply because if he doesn't someone else will.
Anupamaa has been proving again and again that she cannot handle things like independence and having a mind of her own. With added responsibilities like the new hotel and dance academy, she still keeps going back to the kitchen and working as a Shah housewife.
Many people have discussed this enough that Anupamaa probably didn't want another child but agreed to keep Anuj happy, but she has already done innumerable things for almost everyone on the show which she didn't need to. And Anuj to wait for Anupamaa to automatically understand what he wants is very far-fetched, before she attempts to do that she will have another person demanding her time and she will happily agree to it.
Though it may not be considerate, but I'd rather have her say "yes yes" to Anuj's wishes of having a family or swearing not to sign off the property to anyone, than to HasLee's patriarchal tantrums or babysitting for KinTosh or tolerate Ravanraj's taunts with the skin of a hippopotamus.
What do you guys think?
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