I believe that on average non-tech companies treat their employees better and give them more right and freedom.
With non-tech companies you usually sell your time. But with tech companies you sell your brain power, if your side projects affect your brain contribution to that company for sure they don't want that.
So silly of them, I always say this. Companies should stop treating their employees as assets.
And let me say again, there are successful tech companies run by smart people that don't do this! And most employees including the founders are happier because of it.
At SunSed we believe that we should treat business like a passionate music band — making money is not the ultimate goal — the ultimate goal is to see people enjoying your music while you enjoy playing!
Programming all day at work and then spending a lot of your non-work time programming too could put you at higher risk for getting burned out on programming. Spending your non-work time rebuilding old cars probably won't affect your programming at work.
Note that I'm not suggesting that the boss should be able to make you stop programming at home. Many people can program at work and at home and not get burned out, and it should be up to the programmer to decide if they are such a person. I'm just saying that programming related hobbies are more likely to affect programming work than are non-programming hobbies.
Of course, take this with a massive grain of salt. I'd certainly prefer not to have to go to court to try and figure out if this is actually true.
"For example, the California Labor Code stipulates that regardless of what an employment contract or PIIA says, an employee owns the copyright and patent rights to his inventions if the invention is made entirely on the employee’s own time, without using any of the company’s equipment or technology, as long as the invention (a) does not relate to the company’s business, or (b) did not result from work performed by the employee “as an employee” of the company. Washington state has a similar law protecting employee projects outside the 9-5 bounds."