Looking through the top 200 commanders on EDHrec he's the literal only one I don't understand the appeal of (Hell, I've built 11 of them), Atraxa is an alright home for any miscellaneous cards with the word "counter" on them, Meren is an old-guard card and uses experience, Kinnan is cEDH viable, but I can't find or think of absolutely anything for Kenrith other then Eldraine Vorthos or Zirda companion (Hell, with Zirda, Kenrith just looks like a less interesting Marath, and that's not exactly saying nothing). Even his Rec page is just Biomancer's Familiar, Zirda, Agatha, and a list of staples

Edit:

The reasons appear to be:

• He's just about the best infinite mana payoff you could ask for
• One mana to give any player's board haste+trample is cracked
• He's a solid standalone card if you don't want your commander to be in any way important to your gameplan
• He allows 5 colors while only requiring white (With all the other commanders who do something similar being either very specific or much worse)
• Some people like playing staples???