I'd imagine it's because people who use spaces are either further in their career in average (because the modern programming ecosystem in general uses tabs so new devs are more likely to only know that) or they're just more serious about software development because the kind of person to die on that hill is also the kind of person who is very obsessive about other things as well.
Totally agree, all my { end up on the next line, 1st spot when starting a function, last character of the keyword when starting an if/for/... section. I even put the closing one on the same line when it's single line, else either at the end of the closing line (when changing really old code) or same indent.
So indenting varies a lot, which makes most 'new' programmers go mental.
while (my code)
{ I'll do it my way }
if (! liked)
{ toughen-up }
else
{ get used to it
multi-line can go both ways...
}
I use tabs because I prefer 4-space indents and others might prefer 2-space indentation or the gross and unacceptable 6-space indentation.
If more than one person is working on a code base, there will likely be more than one preference, and with tabs everyone gets to just set their own tab width.
Generally aligning stuff isn’t nice. But if you do, it’s tabs up to whatever level of indentation you’re at then spaces the rest of the way. So you wouldn’t have to assume a tab size. And the tabs and spaces have different semantic meaning (indent vs alignment) so mixing them makes sense. It's even built into Jetbrains IDEs, where it's called "Smart Tabs".
Although really just adding a level of indent is better than aligning.