An painter spends 18 months creating a great work of art, one of his best. After he is finished, a guy buys it for a large sum of money and promptly burns it. How does the artist feel? Is he going to be motivated to spend another 18 months on his next idea, even though his previous idea was a financial success?
And if the process is pure tedium and you learned nothing about yourself or the tools throughout it, you should try to create the tools that do inspire you to perform the tasks that don't. Manually creating a production build is boring and you rarely learn anything, but creating a good task runner can be incredibly satisfying.
Edit: Another example with something temporary would be spending time making food for someone who consumes it, versus spending time making food for someone who just throws it in the trash.
Out of topic, but in some countries, it's illegal (https://en.wikipedia.org/wiki/Moral_rights)
Those poor nuclear physicists and rocket engineers -- thousands of them -- in the US and the Soviet Union whose ICBMs and nuclear warheads were never used!
In the case of the game industry, you still got paid, but markedly less than a comparable software engineering job outside the game industry and with poor working conditions in general. This is tolerated because you're invested in the work; when that work just gets thrown away, you might as well have been working on the next Facebook for Cats and making the correspondingly at-market/inflated salary.