AndreyT

Not sure what "leaving orbit" is supposed to stand for. Or what's its relevance in the current context. For example, ISS is in space, however it does not "leave orbit".

In any case, orbital flight is a matter of speed and speed only. Altitude is just a consequence of that speed. The only reason orbital flight is performed at space altitudes is that the absence of any notable atmosphere makes it easy to maintain the necessary speed.

The altitude that defines the "start of space" is a matter of fact, not a matter of someone's opinion. I.e. those "many", they simply don't get to "consider" anything in that regard. They either know or don't know.