Prob because you quit for a while, and while you did, these other guys placed at some tourneys? idk, sheik is kinda scarce unless you count pocket ones lol. Billy seems to get stumped on a couple of MUs haha, but does pretty well in others.
Havok said his sheik was pretty good when he went down there, and he has a couple of decent videos with his sheik (like against Jerm's TL). That being said, I do think both could do with some consistency.
I think Lucario is very dependent on Lucario's playstyle, I personally love choking up lucarios in sheik's strong zones and scaring them (I sometimes use Sheik on lucarios in our area, but depends on which ones), but I haaaaate it when they play really smart with spacing and feints, and it's really scary to throw needles at a certain percent because of high aura AS (not to mention it's a nasty landing trap if the Lucario's good at using it). Oh yeah, and his uair is just nasty against us if he starts a juggle (kills pretty early even with moderate aura, and if you dodge it he can dair you out of your air dodge or even ff -> AS like I've seen Trela do). His aerials in general are really good if you try to fight them, although the dair is fun to bait at times (I've did a gimp once by sweetspotting a double jump fair once when the lucario daired right above me then edgehogged)
I actually haven't seen Tree's Falco in any videos lol, then again I didn't search falco up much haha