You'd be surprised how many people (not on HN) use extremely weak (or no) unlocking mechanisms for their devices. It overlaps with the set of folks who would want to use LastPass because of how easy it is.
Well, I have several family members that fall in the "I use a pattern to unlock my phone or do not use anything to lock it, but store passwords in Last Pass" category. So I guess you're wrong.
I'd be surprised if there was any overlap at all where you claim.