service terminated squawk 1200

I'm curious how important it really is to punch in 1200 as soon as the
controller instructs squawk 1200 as you approach for landing at an
uncontrolled field. I've always blown it off and just landed with my
original code. My thinking is 1) Of the things I need to do to
configure for landing, watch for traffic, get the plane slowed down,
etc this is way, way down on my important to-do list 2) What the heck
can ATC care anyway, are they going to reuse that code in the next 2
minutes 3) If something did happen to me, maybe they'd have a better
radar track if I'm still on the old code??

Im just curious from controllers how important is this change in code
before landing.

-Robert, CFI