Originally Posted by
jet sanchEz
There were no sealed bearing cartridge type bottom brackets until recently so, rather than having grease get all gunked up in the bottom of the frame, cutouts solved the problem. You don't see them on track bikes because grease on the track would be a bad thing.
Sealed bearing bottom brackets have been around for over half a century but didn't become common until relatively recently. Cut-outs are more a vanity thing -- something the builder does to distinguish their frames from others.