I'm male, and DD has my surname, and I actually agree with you OP.
DD wasn't exactly planned, she turned up unannounced 12 months into mine and DPs relationship (literally, we didn't know DP was pregnant until she went into labour). As a result we were still in a fairly casual relationship. We weren't living together, probably only saw each other 3-4 nights a week. Naming our kids certainly hadn't entered the discussion at that point, in fact, neither of us particularly wanted children.
We took weeks to find a first and middle name we could agree on, and then the night before we registered DD we suddenly realised we hadn't talked about her surname. I'd assumed it would be DPs, after all we weren't married. DP on the other hand was more traditional and wanted it to be mine. I didn't argue against it because of two reasons.
First - While we weren't married (and neither of us particularly wanted marriage), I figured we probably would be at some point, if the relationship went well.
Second, DD's name would have sounded bloody stupid with DPs surname. It sounded like a superheroes girlfriend. Think Lois Lane, Lana Lang, Pepper Potts.
We should have double barrelled, but in the chaos of those first few weeks, it just didn't even cross my mind.
18 years on, and I wish we'd done things differently. I underestimated DP's aversion to marriage, so we're still not married now, so she still has a different surname to me and DD.
DD is a lot like me, she looks like me, she has a similar personality and interests to me. I can see all the ways she's like DP as well, but other people often don't, and more than one person has assumed DP is her Step-mum, including class teachers. It doesn't come up much, but I know DP sometimes feels a little disconnected from her, and I think a shared surname would help with that.
Personally, I think double barrelling should be the default when parents don't share a surname, or if not, then it should be the woman's surname. While it shouldn't be the case, on average the mother still generally does the majority of the parenting, and is still generally the default parent if the couple split up., so it just makes more sense for mother and child to share a surname.