Sure, but it's also possible that that core audience is only ~7-10M strong, and that a lot of Series S were sold as secondary consoles not as a companion to a Series X but a PS5 or PC because it's cheap. Being cheap is actually a good selling point which is the whole point of it existing in general.
Ultimately this information will never be known because while I'm sure Microsoft has some sort of numbers pertaining to this they have no reason to ever do anything with it.
Everybody that I know personally (obviously a small sample size) that has a Series S bought it because it was cheap and a way to play Game Pass games alongside their PS5 or bought it for their children. Now there was a time when I owned both a X and S but it was only because I got the S for $150 from Verizon.
Also a lot of "casual gamers" don't keep a million games installed on their console. Think of all the people out there that only play COD, FIFA, Madden, or Fortnite. They don't need a disc drive and they don't need storage (insert joke about COD storage here).