I lot of people speak many Scots words day to day, but won't necessarily consider themselves to "speak Scots", or even realise that the dialect they speak has an official name.

To test this theory, I just asked my mother in law (who is from the central belt) about Scots, and she replied, quite seriously: "Whits that? I dinnae ken whit that is, I spik proper!"

(I'm Scottish, from the North East)