Because manually triggering interrupts to change state in RAM and kick off DMA to drives and bus devices (like network cards) is tedious and slow.
What are you trying to get at?
and toggling in programs from the front panel is tedious :-) (had to do that on a PDP once)
I use OS X, I think they got a lot of stuff right like key combinations are nice and feel more "first class" than Windows esp. with software like spotlight or alfred. It's not a very good experience overall, lots of stupid stuff like Finder, buggy updates, buggy software (not always apple's fault).
I tried not to use it but the darn computer won't operate itself!
at home, direct x.
at work, vsphere client , excel, visio and occasionally, i run yosemite in virtualbox to run application loader to upload an ipa file..
otherwise most of everything else is rhel or centos. doesnt matter at this point which os.