Work is an end in itself to the extent it advances the doer, in the same way that an artist may grow without sharing what is created.
Also similar, there is no obligation that the work or product of it be valued by anyone else.
Without benefit for the doer, nor a result of value to others, it is a waste. Work for work's sake alone is folly.
There is much confusion on this subject, from the labor theory of value to shovel punishments to resentful starving untalented artists.
Not to be confused with work that results in a reserve that can be expected to be of value later, such as is the case with Bitcoin and pushups.