While I agree with you personally, I could see the counterargument of: A tab is always a tab, and I can tweak my IDE to render a tab as however many spaces I like (2, 4, 8, etc) without changing the code.
Sure, IDE's are easy (though many people use multiple IDE's and/or editors across multiple machines).
I've also got a couple diff tools, a few VCS's, also the online parts of VCS like web-based pull request review UI's.
Tabs also tend not to play as nice with vertically aligned elements, if you prefer that for things like say the '.' on multi-line chained method calls, or longer function parameter lists.
I'll work without complaint or changing it with any existing code whether spaces or tabs. Mix the two for indentation however and fixing it is the first commit I make before touching anything else.