Can anyone tell me the purpose of these holes & indentations in the OEM rear bumper (inside the bumperettes) of my 95 YJ?

lol they dont do anything, im guessing jeep just got bored and put them there.

nice drain holes for water that gets into the frame...I spray used motor oil into them after cleaning out the frame from wheeling.

yep them the drain holes...since jeep desided to go with a boxed frame, you can thank them for all of the rotted frames out there

Doesn't seem like it would drain very well with the holes being that high. Maybe during manufacturing those holes served a purpose. Probably so that it would be easy to install something else? Or the previous owner put them there for other reasons?

Weight reduction you must have an early form of a jeep wrangler sport

^^ lol, that made my day

as in regards to the holes, there on every wrangler I've seen. it so you can attach aftermarket bumpers and stuff there when your bumperetts get ruined and you want a different bumper.