A stapler is a practical object — it has a use. A hand-crocheted stapler cozy designed to keep a stapler warm at night? Not practical at all.
The word practice, in the sense of "doing," is embedded in the word practical, which is all about "doing." "Is it practical?" means, is it good to do this? Does it have a use? Will it work? Silk shoes in a rainstorm? They're just not practical. A London Fog raincoat? Definitely practical.