Since many other cases were already covered, I've added this only to show that the possibilities are many.
Legacy vanity addresses are uncompressed addresses and they are of larger size (or maybe the one that I have used in the past) which makes transaction fee to be higher than that of compressed legacy addresses. I think the solution to use lower fee for transaction started as uncompressed address was created. Although, some people may just like to customize their address and they will prefer to use vanity address generator for it. But there is also segwith vanity address generator.