It's funny you say that Arthur, a lot of us who prefer female Robin like her precisely because of her attitude haha, just as Folt says. But isn't it unfair to us that just because male Robin is the first skin that he should be used more often? One of the greatest things about our character is that they're available in both flavors, both in the source game and in this one; trying to make one gender more official than the other outside of personal preference (like the FS and jumping youtube videos you mentioned, which were random personal preference) is kinda like saying "screw you" to the other side and limits Robin's uniqueness as an avatar. You guys already got the CGI character intro in 4, the amiibo, and the first character slot, isn't that enough?
If anything you should consider yourselves lucky, I feel like it's the female Robin players that get screwed over more often when it comes to that stuff.
You brought up some good points Folt, and it's things like that that indicate male Robin has plenty of fans on his own, through the various games. Now the more interesting question, to me, becomes, "Why is male Robin more popular in Heroes and female more popular in Smash?". My guess would be something to do with a higher ratio of girls playing Heroes, since Smash is a fighting game I feel like there is a good percentage less ladies playing it compared to the easier-to-access Heroes. But there could be more to it, like stats and stuff, but I didn't play much Heroes so I don't really know.