There are jobs the electric tools can do that human muscle can not. Try boring a quarter inch dia. hole through an inch of case hardened 4140 chromemoly hand drill and get back to us.
Or just will do massively better and faster - I just had to drill through 3 layers of masonry to run new lines at work. I'm sure I *could* have done it manually, but the hammer drill I had did it with a nice clean inch wide circular hole in only a few mins. The best tool for a job is the one that lets you get it done right, get it done fast, and move on. It's nice to make sure you have a manual backup around, but electric tools get the job done for most people.
Add to that that then you're competing on bandwidth on the PCIe lanes for access to the card's memory with anything you're actually using the card for and it makes no sense to bother.