Even back then we were looking for alternative mouse drivers with lower memory footprints, though =D some wouldn't load high (or not work im games when they were). Conventional memory was such a precious resource in DOS. With a bad mouse driver, you might've had to choose between having sound or mouse control in your game.

For emulated systems, I mostly use CuteMouse now, which occupies less than 4 kB. It sure would've been nice to have had that back in the day.