Well, people just have twisted views of what locks are. To the layman, there is a difference between matted, and tangled hair. They think that dreadlocks are twisted, therefore tangled, but your hair is not twisted, therefore it is just matted.
They don't get it that tangled and matted are the same thing. Try explaining to them that your hair naturally twists and tangles itself. You don't have to do it to your hair.
If all you say is that you wash, people automatically envision clean, straight hair. They might look at you, and see locks, but that not what's going on in their minds. It's a form of change blindness. They are seeing what they are imagining. It's hard to explain. It's like day dreaming while your listening to someone talk. You hear the words, but have no idea what they just said when they stop talking.