Whenever character usage is tracked down, they both end up in the top 25 or so which is pretty good - of course tracking like this is limited to tourneys, but these are two low tier or anyways difficult to win with characters, the high usage rate is easier to explain with people just liking to play as them.
Yeah I would not be looking at competitive tourneys for usage data. The sample size is gonna be way too small and not reflective of the wider playerbase.
Also, a character being lower-tier doesn't necessarily let you conclude that their usage is due to people liking them. A lot of usage is dictated by perceived strength rather than actual strength; if they're getting high usage but not performing well, it could very well just be that there's a bunch of players using them because they
think they're strong, or because they think they can have success with them by way of surprise gimmicky/joke/anti-meta strats.
Maybe I misunderstood your initial point, but that's not what I was talking about. What I meant is that Captain Falcon, Ness, Sheik, Jigglypuff etc. are considered "Smash Staples" because they all fall into some combination of being played a lot / being meme'd a lot / being hyped a lot / offering a particularly unique or somewhat archetypical playstyle, like Sheik does for fast, combo-heavy fighters. How notorious or relevant they are or not are outside of Smash doesn't really matter. This can happen to any character of course, the only requisite is clicking with players.
The thing is that I see this "Smash staple" argument for pretty much every single vet, especially longtime vets. The effect just doesn't seem to be the result of anything special about any particular character, it just applies to everybody because, as it always gets said, "every character in Smash has their fans."
In my opinion, it doesn't seem super productive to devolve things into generic labels like that which are only weakly anecdotally supported at best. I do think we should give characters credit for their popularity, but the "Smash staple" argument is difficult to make without just giving everybody an arbitrary boost simply for having been in the game for X number of years.
On the other side of the coin, a character like Lyn or Skull Kid who is able to maintain such high popularity within their series' fanbase for so many years without being playable in Smash is something to be valued and commended.
But anyway, when I'm saying certain characters compare favorably to several already in Smash, I mean they're not any worse in notoriety, popularity within their respective series, or potential to bring a new dynamic to Smash's gameplay. Simply put, they're just as good of choices as lots of the ones we actually did get, with just as much potential to become beloved members of the cast should they be added, and from that angle I don't think you can say that we're running out of options from older Nintendo, though like I said there is also a wealth of options from more modern Nintendo, as well as choices who represent both.