First, I don't want to type <shift><semicolon><period><space><shift><1><s><h><enter>. I want to type at most two characters, because I do this a lot. I chose sx, but really any good <leader><foo> combination would be fine. Note they're both on the same hand; I had pretty bad rsi for a couple years and was typing almost exclusively with my left hand.

Second, :. !sh eats the command. I want the command to remain in place in the buffer. Imagine you have a buffer full of useful commands that you use repeatedly with minor tweaks, and you use the output of those commands to write other bespoke commands, and so on.

Third, :. !sh leaves you sitting above the result of the command. I rarely want to be there. I want to be positioned right after the result, on a new line, like my buffer is a shell-- I see the end of the result and can immediately begin typing the next command.