That makes sense for someone who highly prioritize security. But average would just download wallet software from certain place (e.g. Snap on Ubuntu or Google Play on Android). And FWIW apt should reject unsigned package or package with invalid signature.
What is stopping someone from adding their own signature to the package?
It's not a big problem with other app stores since they show the developer or company name in big bold letters, so forgeries are easy to spot. But most crypto wallets are made by unknown people, and additionally, there is no way to verify that a Snap package signature really does sign an authentic package, because the real developers are not on the platform.