No language as drastically different from the mainstream as Haskell is will feel pragmatic to someone who is unfamiliar with its paradigm. So I think it's perfectly understandable that you feel that way. It takes substantial effort to get out of the local optimum to find a better global one.
If you define productive as the number of lines of code you are able to write in the next month after you start learning the language, then Haskell will probably not be more productive. But if you define productivity as the amount of time it takes an experienced Haskell developer to build an application with a certain defect level, then I think Haskell is indeed more productive. And I believe this phenomenon becomes more noticeable the larger the project. Purity completely eliminates entire classes of bugs and allows you to be much more confident about the behavior of code when looking at it in isolation. It also substantially improves code reuse for the same reason [1].
Writing new code is one thing, but maintaining existing code is an even bigger area where I think Haskell has higher productivity. Haskell allows me to fearlessly refactor code in a way that no other language I've used comes close to. Purity is a big contributor here too.
There are probably certain classes of problems for which Haskell still needs improvement in the library ecosystem in order to compete. But I'm in this for the long game and am willing to deal with this in order to get to a better capability over the long term. The ecosystem has surprising depth already and is growing quickly even though the community is still relatively small. For instance, a relatively recent improvement is that Haskell now has more complete OpenGL bindings than any other language [2].
So in short yes, there are definitely people who use Haskell because they believe it makes them more productive. I personally believe this is related to its elegance.
If you define productive as the number of lines of code you are able to write in the next month after you start learning the language, then Haskell will probably not be more productive. But if you define productivity as the amount of time it takes an experienced Haskell developer to build an application with a certain defect level, then I think Haskell is indeed more productive. And I believe this phenomenon becomes more noticeable the larger the project. Purity completely eliminates entire classes of bugs and allows you to be much more confident about the behavior of code when looking at it in isolation. It also substantially improves code reuse for the same reason [1].
Writing new code is one thing, but maintaining existing code is an even bigger area where I think Haskell has higher productivity. Haskell allows me to fearlessly refactor code in a way that no other language I've used comes close to. Purity is a big contributor here too.
There are probably certain classes of problems for which Haskell still needs improvement in the library ecosystem in order to compete. But I'm in this for the long game and am willing to deal with this in order to get to a better capability over the long term. The ecosystem has surprising depth already and is growing quickly even though the community is still relatively small. For instance, a relatively recent improvement is that Haskell now has more complete OpenGL bindings than any other language [2].
So in short yes, there are definitely people who use Haskell because they believe it makes them more productive. I personally believe this is related to its elegance.
[1] https://www.youtube.com/watch?v=BveDrw9CwEg#t=933
[2] https://www.youtube.com/watch?v=yFXzuCFeRGM#t=7292