In the books both in the Old Law and in the New the men who repented of their sins bestrewed themselves with ashes and clothed their bodies with sackcloth. Now let us do this little at the beginning of our Lent that we strew ashes upon our heads to signify that we ought to repent of our sins during the Lenten fast.
~Ælfric (Anglo-Saxon, 10th c.)
A few years ago I went to Mass at Noon during my lunch hour. I went back to my job at the car dealership repair department with ashes on my forehead. All day mechanics kept telling me "you got grease on your head". It gave me an opportunity to tell them that Lent was starting and this opened the door to talk to them about the Lord.
Last year I was at the library and noticed someone else with ashes and we said hello. It's nice to recognize fellow travellers.