do you still say "THANK YOU" to someone?

I do say thank you a lot and usually only if I'm happy with some kind thing someone does, like holding a door open for me, or doing their job with a smile or going out of their way to help. Sometimes I say it to someone when I'm actually being curt because, for example, they let the door go and I didn't have time to grab it. I feel the use of the word isn't used much and is seen as old-fashioned and unnecessary...But when I hear children and teenagers using the word, it makes me feel good that there are those who still have manners and appreciation.