Because physical movement is intuitively transitive. Going from A to B then B to C is the same as going from A to C.

The journey from Y to Z might feel more tiring than the journey from A to B, but only if you do them all in one day :)

So why isn't increasing your velocity from A to B then B to C the same as A to C? Isn't that intuitively transitive too?

it is if your reference point is A in both cases.

> Going from A to B then B to C is the same as going from A to C.

Not really, no. Not all forces are conservative.