I play a good deal of Commander. I think more than the average player, but it's hard to really get a good read. Between casual Wednesdays and cEDH Saturdays at my shop and my two weekly regular playgroups, according to my tracking from the beginning of the year, I have averaged around 8-10 games per week. So far I have played 172 games this year.
With a sample size this large, I would have expected to see more of the "top 10 most popular commanders" much more often (even cutting out cEDH night, where they are unlikely to show up, I'm still at ~130 games).
For reference, here are the top 10 commanders and the number of times I have seen them this year.
The Ur-Dragon - 1
Edgar Markov - 0
Atraxa, Praetor's Voice - 0
Y'shtola, Night's Blessing - 2 (same player, same evening, dismantled the deck by the next wek)
Krenko, Mob Boss - 4
Kaalia of the Vast - 1
Sauron, the Dark Lord - 0
Pantlaza, Sun-Favored - 2
Ms. Bumbleflower - 9
Lathril, Blade of the Elves - 1 (My deck, changed to Morcant when ECL released)
I know EDHRec's data isn't perfect, and is scraping decks that may or may not even be made in paper, but it's the data we have, and my mostly useless Psychology undergrad degree still has its hooks in me when it comes to finding out what statistics mean and why they don't always match lived experiences.
My working Theory is a combination of three things as to why people maybe built/uploaded a decklist but do not play it very often.
First: The deck outperforms the builder's intended bracket and lead to unfun games, but cannot hang in higher power games as they become removal magnets or are simply too slow (Krenko, Y'shtola, Kaalia)
Second: They were precons that were played a lot right out of the box, but fell by the wayside for old favorites or when new precons came out (Sauron, Pantlaza, Bumbleflower though admittedly she is my most seen of the top 10)
Third: The decks are simply too linear/unfun to play a lot, and the commanders are old/already seen their day in the sun. (Ur-Dragon, Edgar, Atraxa).
This is very long winded and probably super un-interesting to most people, but if any other stats-minded players with too much time on their hands could sound off I'd love to hear ya'll's thoughts.