What is useful is a subjective concept. It is possible to justify almost everything as useful in some manner.
There are actions that are useful because they create value. For us, or for others. They result in tangible work.
There are actions that don’t result in anything tangible. I once read about a man who went out for a walk every day, and while doing so, made a point of photographing a flower. A different flower every day. The idea was that this was a way of remembering to appreciate the little things.
But what if this man, instead of taking the picture, just smelled it? What is the value of the experience? Is it the origination of a photograph? Is it presenting work?
Will not the act of smelling a flower suffice? Will it not have an intrinsic value, even if only momentary?
Who said that value is only value when it is not perishable?