What are your views on public courtesy?

This question idea arose when today, I held a door open for a man carrying his daughter, he barely acknowledged me, yet alone said thanks.
I like to help people out and will do things such as these in order to make it a convenience for others.

So, the question explanation?
Do you think that it is just common courtesy to show manners and thank people for helping you (i.e. holding doors for you)
I certainly know that when someone holds a door for me, I have to thank them, I sort of just can’t not.
Do you thank the person profusely or walk past them as if they were invisible?
Would you hold the door etc. for someone, or would you let them deal with it on their own

I am just curious about your views, please don’t hold back