Aside from legal issues, this is a complex topic I'm also interested in, specifically for programmer / engineers, or in general people in tech, they are 1) know

Aside from legal issues, this is a complex topic I'm also interested in, specifically for programmer / engineers, or in general people in tech, they are 1) knowledge workers 2) in high demand (market lack of such skills). 1) implies that working is not just about scheduling a certain number of hours per week to a task, it's a mindset thing. You're hiring their brains for an extended period of time on long projects, to achieve a bigger goal. 2) means they have tons of opportunities at a lot of others places. 1 and 2 together in general means they are pretty independent strong minded people (which is a good thing), that they can't be really controlled (which is a good thing) and they can do pretty much what they want in the time allocated to the employers. Clever people on the internet will tell you it all comes down to trust between the employee and and employers.. Of course there is more to it, that's just the starting point of the discussion. How do you create and sustain that whole work relationship is a full time craft for a manager. And then there is the debate between freelancing and employing. Freelancers are perfectly fine with multiple clients, it's part of the thing. But with knowledge employees, they are expected to be dedicated to your company (they don't have specific hours but a general goal to perform and a certain expectation of commitment), otherwise they're just playing the same game than freelancers, in disguise. If you're going to tell me that "its just about setting some KPI / performance metrics, if you cant do that then you're not a good manager" then please don't also tell me at the same time "engineers should be free of all constraints, let them do their thing without any surveillance that's bad for their morale !" in others situations. We have to choose. Either we trust the person is going to be dedicated to us (or will come forward that they want to work with another company at the same time) without hard surveillance, or you're treating them like resources that we can manage, track and fire easily if the performance review is bad. No side of the spectrum is best, where to stop the slider is highly dependent on the situation and people too