Think that has more to do with the background for the hitter.
but if that is the case, you could still have seats say 20 feet up, and I remember a lot of old parks frm the 70s (ie multi use parks like the Vet had seats all around the OF, just the first row was say 25 feet off the ground. batters eye does not extend upwards indefinitely.
and there was a story a few years ago, forget which city, with a guy in CF with binocs, holding up one arm for FB, another for offspeed, think it ended up just being a fan of the home team and trying to give an edge (and how does MLB regulate that