I have never used a desktop wallet because in my opinion a desktop wallet cannot be accessed in various places and we cannot access it at any time because we are not always in front of the desktop, even though it has more features but I think a mobile wallet gives us convenience in accessing it, and we can anytime and anywhere to access it without having to open a laptop/pc first to be able to access the wallet that we have.
You are wrong in giving your opinion about desktop wallets because for the metamask use case, you can import the same wallet in the mobile version of the wallet so it is more practical to use in different conditions, desktop and mobile are just device issues but not for one wallet because both can be imported if using the metamask wallet.