The concept of Mother May I has the inverse concept of Player Entitlement. I can do this because the rules and my character sheet say so.
See, I'm not with you there. If I'm doing something that my character sheet says I can do, that's not "Player Entitlement", that's playing by the rules of the game.
To me, "Player Entitlement" is more like players wanting to use game elements you've excised from a campaign- say, Monks, Paladins or specific spells, etc.- because they don't fit.
If a DM told me I couldn't ride a completely mundane horse despite my PC having great skill in horsemanship (not because i failed a roll, either), I'd walk away from the table. And as a DM, I'd never do something like that.
Again, that's all well & good if you have a DM who can/does do that kind of game management. I can and have done it myself.
But I'm currently running about 50/50 in my 34 years of gaming experience, and let me tell you, it can be quite frustrating when you try to do something outside of the published rules of a game and you get ruling #1 when you do it...and weeks later, when someone else tries it, you get ruling #2.
...or some OTHER kind of response that boils down to the rules gap causing a problem.
Its not like asking for the inclusion of "Starship Piloting" skills to be added into the game. Its
basic stuff- there really is no reason why a FRPG game with a skills system shouldn't have some kind of a Ride skill. And I say that as both a player AND a DM.
Its also not exactly an answer when you have players who don't invest a lot of time in writing PC backgrounds (for whatever reason). My current gaming group has a lot of busy, busy people in it...and one with adult ADHD. I'm damn near the only one who has a background longer than a few sentences.
The last game I ran, I asked for backgrounds. I even did my typical "your background may have an effect on starting equipment yada yada yada" statement.
Out of 10 guys, I got 1 one paragraph background.
And its not like they aren't roleplayers. They're damn good roleplayers (well, several of them)- and not a one with less than a decade+ in the hobby.
Simply put- for whatever reason, if it isn't in a rulebook, they don't consider it as part of character generation.
YMMV- and clearly it does.