Between minifying your css and js, and gzip compression, I doubt that tabs save you a significant amount of bandwidth when you're on your phone.
And how often are you working on code where using tabs instead of spaces seriously impacts your storage and I/O?
You don't keep your source code in a minified state, nor do you keep it gzipped; the storage/bandwidth/IO considerations are for SCM-tracked code where there are potentially many, many copies of the same file in different states.
If you could reduce a 34-line (1KB) diff by 20% (average of two indentation levels of four spaces each across those lines), why wouldn't you?
I also do not access my code on a mobile device.
And I wouldn't reduce it because I have 122 gigabytes of space free on my machine, and absolutely do not care about saving 200 bytes worth of space, even considering it's per commit.
After all, you could reduce your code by even more by minifying it before adding it to your SCM, right? (I know, I know, if you take out line-breaks, diffs will become unreadable).
Saying you don't conform to a use case does not invalidate said use case.