Well it might, but in what calculation would the fact that time extends infinitely be a factor? You can say all past time resulted in the current moment, but as far as I know there's no such thing flowing from the future into now. So any physics calculation you do will deal with finite amounts of time.

I won't pretend to know every possible calculation that might be desired, but I can imagine any sort of prediction or simulation about the future may want to use such an infinite view of time going forward.