It wasn't about bandwidth, but long signatures were obnoxious beacuse you had to see them multiple times per day. https://en.wiktionary.org/wiki/McQuary_limit

People whined about bandwidth waste in this category of complaints but I think it wasn't a real problem, just another aspect of an already-disliked long-signature practice: https://books.google.com/books?id=qoc5DQAAQBAJ&pg=PA97#v=one...