As someone who has the ability to work 2 tech jobs if I wanted to, I could context switch every minute if I wanted to due to the technology allowing me to do so. Why should other people be unable to do this if the tech is there to support it?
No it is not and never was. Sales people - going back a very long time and include fully traveling ones - are not employees? How about traveling service technicians, not infrequently located all over the country, far from any company office? Home office - not uncommonly full time even, e.g. the company I work for does not even have an office but people employed all over this and other countries - are not employees? Please don't arbitrarily redefine "employment" to make your point.
I've seen these precluding secondary employment with competitive entities, but it seems there'd be little competition between Fred's and Alice's businesses (based on name alone).
Why? In America, there are tens of millions of people who work more than one job. They're still employees; just employees of more than one company.
Fred's Plastic Fork Factory can't tell me I can't moonlight at Alice's Diesel Cafe and Firing Range.