Well in the first place I think for the same reason why people want to change the comfort indicator cycle from 3 to 4.
Because it's possible.
This yellow beep tone at startup is quite annoying like "wtf is wrong, engine broken" but nothing is actually wrong
Imagine your horn would give a sound every time you change gears.
@hadez16 changing indicator flashes is hardly a fair comparison to make now is it ?
For one....its a well documented viable working change
As for the cold start warning......you get in press the button car beeps but so what ? it's lost / forgotten about when the 5 pot barks over it.
One beep is hardly an issue.
But as Leo says it highlights this to not so savvy owners.
It helps to give people an awareness of some mechanical sympathy, because everything is cold.....
If i had my way it would stay on until the car is ready for some proper action......