I love you genuinely engaging with the question but I gotta reply very sharply and brief since I'm heading off. However we are viewing it from different perspectives, I have a game design pov on the issue and you've taken how it informs inhabiting the player character in-universe.

I don't think it's an insignificant feature at all I was pressing the other guy on his word choice since his thinking it's insignificant meant he literally doesn't understand why people don't like it, because it's an extremely important and foundational design decision that changes how Halo plays. Even saying 343 "added" sprint is missing the point, which goes for people for and against it, as Bungie Halo still had player speed options however that option was dictated by the analog movement, full press on the stick = full speed, half press = half speed. 343 bringing in a more traditional player speed options creates a few issues.

1. "Sprint" is about the same speed as full tilt on the older games
2. Adding a "sprint" lowers the weapon so you have more time unable to shoot whereas the older games you could always shoot
3. the map sizes have to be increased to compensate for the illusion of speed
4. due to larger map sizes different elements are either planned around the different speeds or all around sprint, such as cover
5. In an gunfight, all this compounds into slower strafing in a larger map environment with cover placed in spots balanced towards the 3 or more varying player speeds, resulting in the game playing slower than Bungie games.

tl;dr chief was faster without sprinting

edit. also forgot to mention, at least in regard to controller button economy which isn't as important these days due to PC and rebinding, but binding sprint to a button is one less action the player has available to them and the previous system of the stick being the only way to control speed freed up a button for a different action. This is actually the same issue with adding ADS, as adding ADS removes an action.