I've been wondering the same thing. I started doing projects that involved parsing during covid lockdown, and since then I've done lots of toy projects and one

I've been wondering the same thing. I started doing projects that involved parsing during covid lockdown, and since then I've done lots of toy projects and one full-sized programming language, and I very quickly realized that a) lexing didn't really make parsing any easier, and b) any non-trivial lexing (eg. number literals) was just duplicating parsing work anyway. It just seems much simpler to have a single layer that consumes characters off the front of a string