I set up my own email server yesterday, and was forced to consider the question of why. The answer I found raised more questions.
Kant's Categorical Imperative states, in a nutshell, that one must always act in accordance with what one could wish to be a universal law. I like to think of it as the law of "no exceptions." You can't justify to yourself that something's ok if you're doing it, you don't really have an impact compared to everybody else who's doing it.
This makes sense re the email server—I believe that the world would be better if everyone had their own email server, if the web was, as designed, decentralized, and we were unbeholden to the few big tech companies that now control so much. My email server right now isn't very useful: the big providers block it so I'm unable to send any mail. However, I can't not run the server, as that would be inconsistent with my beliefs. And, if others set up independent servers, I would likely be able to communicate with them, as I wouldn't be immediately blacklisted due to being a small server. Thus, the more people do it, the more useful it becomes.
But then I got to thinking—whenever people have asked me in the past why I'm vegetarian, I never have a good response. I usually mumble something about ethics and factory farming, and they're satisfied enough (no one needs me to explain the arguments of Animal Liberation, after all). But I see parallels in this with my humble email server. Most people can agree that factory farming is bad, but reconcile themselves with eating meat by thinking about everyone else. "I'm only a drop in the bucket," they think. Kant's Categorical Imperative doesn't allow us to do that.
I believe that the comparison between big tech and factory farming does not need to be limited to the surface level. Both, most people can agree are bad. Both, most people live with anyways, because it's easier or they believe that their individual actions won't make an effect (I'm certainly guilty of staying with big tech companies out of ease and have no plans of moving my main, mission-critical email account off Google). Can this template be fitted to anything else? I'm not sure. Is the common story—that something objectively bad became too ingrained in society, to the point that it would be deleterious to remove it—of any use? Perhaps it is a warning to us—to be more vigilant, to not take things for granted.
UPDATE Feb 2022: Hey, this is why I study Esperanto, too!