My own snap hypothesis would be quite simply that, in this particular holy war, hard tabs lost. Not because they are inferior, in fact I think Go stands as an interesting outlier; they ship a canonical code formatter with the dev tools, and have apparently decided that hard tabs are better iff you can ensure that everyone uses them all of the time and I suspect they’re right. But it seems like in nearly every other language, to varying degrees, people have gotten tired of incessant formatting glitches and decided that whatever else you can say about them, at least soft tabs look the same for everyone.
Except, developers tend to be a picky and opinionated bunch. For my part I work for an employer in another country (and put up with all the paperwork that entails) just because I was adamant about the programming language I wanted to use. And take @caze who (with all due respect) likes his tabs hard, and if you disagree you can “suck it up” and use “better” tools, and if you come at him with some soft tabs he’s gonna fuck that shit up. I mean, I don’t want to infer anything about you personally, caze, I’m sure you don’t vent about this sort of thing at work the same way you do here. But then there’s people like a friend I have who is deep in the autism spectrum, an awesome programmer with his way of doing things and if you disagree then You Are Wrong. He literally spent years travelling the world to find anyone who would let him set up his stack just how he wanted it.
What I’m saying is, developers often have strong personal preferences, and we can be abrasive about it and even limit our employment opportunities over seemingly trivial details. There’s probably just as many such people in the soft tabs camp as the hard, and there’s maybe some of the wage difference that can be explained by soft-tabbers having more jobs to choose from. But also, I suspect the statistically significant difference might come from people like @orenwolf, who like hard tabs personally but in an interview or survey scenario they’re likely to respond “soft” as a way to signal that they are happy to go with the consensus to avoid friction. People like to hire people like that.
Will you convert them back when you’re done? Supposing it’s an open source project, say.