I think you have it the other way around.

It's not used because it's the default font in Figma.

It's the fact that it's the best modern alternative to Helvetica, making it universally useful and therefore the default in Figma.

Incidentally, I'll forever mourn that the designers didn't choose to go with a glyph for "1" that is closer to the one in Helvetica.

Inter is the default in Figma because the first designer at Figma was the guy who created it.

Huh, TIL. Thank you!

I guess I can try to argue that it if it weren't as generally useful as Helvetica it wouldn't have been made the default in Figma and it wouldn't be, well, so generally used.

Hah, this one can go on Wikipedia as an example for "chicken or the egg"! IMO, there's probably a number of other fonts that could've been chosen rather than Inter as default Figma font, and if they had been, they'd now be more ubiquitous than Inter. Of course, we'll never know. Unless someone here is looking to do a research study into popularity of fonts over time compared to popularity of Figma and seeing how strong the correlation is - maybe a weekend project for someone into typography ;)

Oh, is that why everyone uses it? I just assumed people wanted knockoff San Francisco on purpose