Some people use proportional fonts in their IDEs, and have been for decades. It's just not exactly a mainstream practice. (I seem to recall that Microsoft used proportional fonts in their IDEs in the 90's. Or maybe I'm thinking of Visual Basic? Not sure.)
The main reason I have felt no inclination to use proportional fonts when coding is that proportional fonts tend to be _very_ bad at distinguishing homoglyphs and that is the _last_ thing you want when trying to find the syntax error or undefined variable. Although I will admit that I haven't look very hard for a proportional font that's actually meant for programming.
The other reason is that sometimes I read code where someone has created an ASCII diagram in the comments, or have other structures or whitespace where vertical alignment matters. (This used to be highly popular in C, although it's viewed as a bad practice in "modern" times.)
I find monospace code very easy to read, so I guess at the end of the day, proportional fonts have a few disadvantages with no real upside. For me at least.
> I seem to recall that Microsoft used proportional fonts in their IDEs in the 90's. Or maybe I'm thinking of Visual Basic? Not sure.
What's the distinction you're making here; are you saying Visual Basic isn't an IDE? Because AFAICS it very much is. (Or was, whatever. For its time, not even a bad IDE AFAICR.)
The main reason I have felt no inclination to use proportional fonts when coding is that proportional fonts tend to be _very_ bad at distinguishing homoglyphs and that is the _last_ thing you want when trying to find the syntax error or undefined variable. Although I will admit that I haven't look very hard for a proportional font that's actually meant for programming.
The other reason is that sometimes I read code where someone has created an ASCII diagram in the comments, or have other structures or whitespace where vertical alignment matters. (This used to be highly popular in C, although it's viewed as a bad practice in "modern" times.)
I find monospace code very easy to read, so I guess at the end of the day, proportional fonts have a few disadvantages with no real upside. For me at least.