Which is why you design the game that way. You drop in hundreds of sidequests (literally, Ubi's words) to pepper you with XP, but you keep it a tight leash enough to make the sweet offer of cutting the problem in half for just 10 bucks.... you are not actually speeding the process along, you are very much more likely paying to revert it back to it's original leveling up balance.
For players that actually want to speed things along... they will just get trainers or cheat engines to raise the XP cap. They will just cheat. It's their game and it's singleplayer, so who cares? What Ubi is doing here is selling you a XP Trainer boost, just an official one. The difference being that they design their product to allow for that. Nobody makes a microtransaction item not expecting sales. They know ho the mobile market works and how these tiny sales amount to huge numbers down the line, and they made their game fine tuned to poke at that.
This is not conspiracy, we KNOW for a fact that Ubisoft has invested in the past on studies and controlled groups to id the "DLC Sweetspot" for their products. They are not the only company to do that... but we also know that they DO that. Not recognizing this is beyond silly...
You should be doing side content because the side content is engaging and high quality, not because "Im supposed to in order to be allowed progress". And even if that content is good (though i honestly doubt that EA managed to create "hundreds" of top notch side events) guess what? That's not the argument people are putting forward. What is being said is "Just do it like you're supposed to, it's fine" . There is very little "im having so much fun with this i didn't even notice the XP gap".
So... yeah... you guys are the people on the mobile game going "Well, i would rather pay for some crystals than lose all my afternoon grinding this new event to get my drop"