Why do some fonts make the I,l,1 characters look identical?
There are fonts where they don’t just look similar – they are the same exact pixel locations.
Why were they ever created?
I’m guessing this goes back to something historically, for example printing presses where you had to manually possition all the lead blocks for each page.
So if you had many characters that could all use the same block then it was a saving instead of needing 3 sets of blocks for 3 characters, maybe you could get away with 2.
Does anyone know for sure?
Characters that could be interchanged, indeed, would save money in the days of moveable type.
That said, the ‘1’ and ‘l’ were given spots in the typical job case:
When typewriters came along, the mechanics dictates that the fewer characters meant the fewer bars needed, which was a huge benefit giving the limited space. As such, early typewriters omitted a ‘1’ key, as the ‘l’ would suffice.
Today, with digital type, there’s no reason whatsoever for characters to look identical other than aesthetic choices or just old habits. It’s obviously easier to cut-and-paste rather than design unique characters.