In Star Wars the bigger part of rebel fighters are named after a letter, e.g. A-, B-, X- and Y-Wings. This pattern does not carry over to fighters of other factions. (E.g. a TIE fighter could have easily be named H-Wing, but is not).
Is there any in-universe or out-of-universe explanation for these names?
I am not looking for the answer that they are called that because they look like a letter, but rather the answer to why this type of naming exists and exists only for rebels.