It mostly concern artists that present video such as for art exhibition or VJ live shows I believe. Any unintended visuals would kill the immersion, the aesthetics and looks unprofessional. Like leaving the mouse cursor visible or UI elements.

I see that some people above suggested a solution with an extra hardware device but even though a lot of theses creatives are using macs, they aren't especially tech literate outside of their field and have to make do with venue that can use quirky hardware with sometimes very limited time to set up their gears.

This dot is a major pita for these users.