If you shoot a deer in the woods there will be a time interval before you get it to either a butcher for processing or take it home to do it yourself.
The meat you get at the grocery store, not to put too fine a point on it, has been dead for days already. It has already “used up” a lot of the time until it’s no longer fit to eat. Something just killed should be processed as soon as practical, but it’s not an emergency and it doesn’t have to be done in an hour (though it’s great if it can happen that fast). Field dressing removes the greatest spoilage hazard, after which the carcass is not only lighter but has some time before it goes bad.