I think this is a good read to learn about what tabs and tabstops really are regardless of whether you agree that tabstops should be at different positions per line or with the controversial idea of using proportional fonts (this would work with monospaced fonts too).
Yeah, I personally don’t like aligning key value pairs all the time (maybe rarely I do). The most compelling example is putting a tab before end-of-line comments. Also it would make tab delimited CSV files render more easily.