To be honest the breathtakingly ignorant posts wittering that you aren't a family if you don't share the last name or that you are housemates that share a child should be pitied more than anything, I mean that's an outstanding amount of insecurity to honestly dismiss other people's families that way. Consider how depressing it must feel to believe the only thing that unites you is a name? Not like, commitment which doesn't require legality....nope just a name.
I want to clarify I mean that only for those who put down other relationships for not sharing the same name...that is truly quite sad.
People have different reasons. I was married before my DC were born. The marriage ended after. I have kept my exdh name for now because for my DC personally (not the same for everyone) it helped them keep a concept of family when everything else was changing. They struggled at very young ages not to feel like they were losing their family.
Now many years on , we have a different unit. My DP has proposed and I am considering the name situation now. The DC are old enough to understand what the family is (and they absolutely see it as a family) however I am now at the age where I am rather sick of having my fathers name or my ex husbands name or my future husbands name.
I'm personally a little tired of having to use a man's name. However for a long time it was absolutely important for my DC that mum had the same name as them. I couldn't car else's for any faux head tilting confusion over why, it's not a great leap to realise different circumstances work in different ways. It's not something people don't understand its that they think that by wording it as something confusing makes people think they are right.
It's incredibly simple. People do what works for them and its got absolutely nothing to do with anyone else that doesn't share that name.