Thank you. There are a few reasons I didn't go that route.
1) It's a retro-style game, and this was a very common control scheme for old games (e.g., Combat on the Atari, Wolf3D, etc)
2) It's developed in PICO-8, which doesn't really allow for mouse control (unless using debug mode, which isn't supported in browser)
3) I dislike games that require you to use both hands (mouse + keyboard) when one hand is enough to cover all the controls. Requiring only one hand rather than two can make your game more accessible, both for people with physical restrictions and for folks using laptops without mice (like me!)