Ironically, Apple had a single button reset (labeled RESET) on the Apple II. People pressed it by mistake often enough that users often did things like remove the key-cap to prevent accidental presses. Later on, Apple put a heavier spring under the key to force you to press hard. On the IIe and //c, they forced you to type Ctrl-Reset, in order to eliminate the problem. (And to reboot, it was a 3-key sequence - OpenApple-Ctrl-Reset).
Interestingly, many versions of Mac OS supported CMD-CTRL-Power as a quick-reboot sequence as well.
In the Sun workstation world, the critical keystroke (to pull up the system-monitor shell) was not just the "stop" key, but was STOP-A - another 2-key sequence.
Gates may have wanted a single-key reset button, but other manufacturers all learned that this was a bad idea and migrated to 2- and 3-key sequences.
Ironically, Microsoft chose to stick with Ctrl-Alt-Del on Windows XP and later, to bring up the emergency features (logout, kill processes, change password, etc.) even though at that point in time, there was actually a key dedicated to that purpose - Alt-SysRq. A key which almost nobody used for anything (and has been removed from many modern keyboards.)