Why are Hardware and Software (which is programming) questions off limits when both are fundamental aspects of Computer Science. Since they are off limits, is there a stack exchange community dealing with Hardware and actual programming questions?
As you might guess from the name, this site is about computer science. Note the word science. Science does not include engineering or technology. The science underlying computer hardware and software is on-topic, but not hardware or software engineering, nor how to use computers.
Likewise, it sure takes some physics to build a car, but if you want help with tuning your engine, that's off-topic on Physics and on-topic on Motor Vehicle Maintenance & Repair. And if your question is about using a car to get from A to B, it might be on-topic on Travel.
There are many Stack Exchange sites about computer technology, including sites about programming and sites about using software and hardware. (Programming is only a subset of all software topics!) See the big list on the main meta site.
The interplay between Hardware and Software is a main field of Computer Engineering and as such, a part of Computer Science and a part of this site.
Programming by itself is off-topic since the StackOverflow site covers this topic. Hardware by itself may be more appropriate in Electrical Engineering but, IMHO, is on-topic here as well, as long it is computer hardware with relation to computer behaviour and performance.