The answer to your question of why people say no to popular names is:
1. they are unaware of the statistics or
2. if they are aware of them they don't understand them and/or
3. if they understand them the feel so traumatized by past common names and have been so indoctrinated into society's obsession with uniqueness and singularity that they choose to ignore statistics
4. or a combination of 3 and just liking weird names. Though I honestly think more people rationalize the truth of 3 with 4 since they're really spins on the same thing.
Names do sound less "exciting" to me when I hear them a lot, even if I love them. For the names in my signature, I know four or five Victorias and while I still love it, it's not as thrilling to see or hear any more. Personally I prefer more unusual names, yes, but unusual as in I haven't/don't hear them all the time rather than what's statistically popular. Canadian popularity charts are unfortunately not easy to find and not as detailed (or helpful) as US ones, but in the US my name was top 20 or 30 for the year I was born and for most of my life I didn't know any.
That being said, I would use the names I loved most regardless of popularity. Uniqueness/rareness is nice, and maybe that would make me love a name more, but if my favourite name became #1 I'd still use it. As you can see from my signature, some of my favourite names are top 100 and some aren't even in the top 1000 at all. I haven't met many people- or anyone- with most of those names though. I love my top 4 (Azalea, Sebastian, Cordelia, Fitzwilliam) so much and have for so long, and they all have personal meaning to me, so I couldn't see myself falling out of love with them too easily. But *shrug* who knows, and it'll be at least ten years before I have kids anyway.
Realistically, I get all of that. But I'm still turned off by most "popular" names. I wonder if some of it comes from being active on parenting message boards/facebook selling page. On my FB, there are about 15 Harper's. I used to love Harper but now all I think of is "too common". I doubt there are 15 Harper's in my small town but I just don't see it that way.
I have been guilty of dismissing a name just because it's too popular. Then again, the heavy hitters of the top lists these days are names I genuinely don't like anymore - Olivia was a favorite of mine back in high school but now it just makes me yawn. I never did like Isabella. Ava is pretty, but meh. I think I'm more guilty with boy names. My dad and I were bandying names about the other day (I'm not even pregnant yet, ha) and he suggested William, which I immediately shot down. However, it stuck in my mind and I realized that even though it's William - super common and all - it's still a great name with a lot of tradition. Now I love it.
I think my tendency to do this comes from being referred to as FirstName C. for the majority of my childhood. ;)
I think that for a lot of us naming children today, we grew up as one of the kids who always had to have their last initial attached to their first name. For example, my husband is Matt and there were even times there were more than one Matt B in his class/ group! So of course he wants to avoid that for his kids.
But for me, it isn't the popularity that decides it. We just decided we wanted names for our kids with clean slates, no associations with people we knew. Since we know lots of kids now, it naturally eliminates lots of popular names we liked. But some not so popular ones too.
We live in Canada where
my first son Sebastian is in the top 100
my second Oliver is in the top 50
and my daughter Harriet is NEVER heard
But we didn't know anyone personally (at the time) with any of the names, and we loved them all. So, I guess it's really a combination of factors that help us choose our names. So far, Oliver has only been Oliver R in one play group-- so who knows!