Round our way (Sheffield) I notice people tie ribbons and leave flowers on trees in memory of people, not always at accident spots ( teddy bears etc !)
Over the years other rpeople add to them even if they don't know what it is for . That seems to satisfy a basic urge to give thanks for a life in general or just being there or here. Like cairns in the hills.
In time such decking a tree or a significant site can become a tradition and even a cult or part of a religion which is passed on as new religions are adopted or imposed so such accretions become strong traditions .
Will we all give thanks if we survive today!? People are going on about it like there'll be no tomorrow but still rushing around buying presents.