Unproductive complaints are... frustrating if you're on the receiving end of them, because they are basically (and unproductively) asking for help / solutions. But if it's just complaints, they also have the impression that the problem is not in their "sphere of influence"; coffee, for example, is usually handled by a facilities department. It's easy to complain about coffee to your boss, but it's confrontational if you actually pull the issue into your sphere of influence and go to the facilities department to complain.

It opens you up to vulnerability. You speak to people you don't usually speak to; you get confronted with the realities of that particular issue; office coffee for example is often a factor of budget vs cost, long-term supply and support contracts with coffee machine companies, and of course personal taste. Are you going to take on some responsibility for all that?

Of course, the other part is that you get hired for one job, stepping outside of that role to pursue something not directly impacting said job is often frowned upon. I say often because it's a bit of both, the best people will take on more and different things than what they were hired for.

Anyway. Complainers can / should get a training about "circle of influence/control", also because I doubt that work stuff is the only thing going on in their life, it can help them outside of work too. Knowing what you can change and what is outside of your control is great for your peace of mind and general attitude.