But then again I wouldn't buy anything that didn't lock up so I wouldn't really know what goes through the mind of a FF consumer
It seems that you don't realize that a friction folder is a lockable knife when the lever has enough length like the one of the De Leeuw's design.
I don't trust any locking mechanism, except Opinel rotating ring and my hand. With a friction folder, my hand's palm or one of my fingers is a part of the locking mechanism.
Most of the time, the lever will hurt your skin way before the blade is supposed to close. You receive a clear signal / alert, contrary to a back-lock, liner-lock, frame-lock knife that is going to fail.
A friction folder can be more secure than any of your knife with a "lock up".