In old-style figures, 1 only goes up the x-height, so that wouldn't work. But even in "typewriter" typefaces on computers, 1 and l (el, not eye) look pretty close. And the difference between O and 0 is mostly the width, which is fixed on a typewriter anyway.

I've still encountered text on the Internet that substitutes I for 1 and O for 0, presumably written by people who learned in an earlier era and haven't shaken that habit.

But it's slightly hard to search for because a lot of the search results are OCR errors. Still, I'm sure not all of them are because I've seen this in newly-published news articles (maybe written by journalists or edited by editors who've been in the news business for some decades?).