Palm programs tend to be small and lean, focusing on doing one thing and doing it well. Compared to other processors (e.g. RISC chips such as the ARM processors common in other PDAs) the binaries tend to be noticeably smaller. In addition, because of the design of the Palm OS, applications can be "executed in place"; there is no need to copy a program from "storage" into an "execution area".
These and other features add up to an efficient tool. Eight megabytes is a lot of space if you use it right. I have loaded up a great deal of information and have yet to feel cramped on my 8MB Palm unit.