I think it's partially nostalgia, a bit like looking back on an old girlfriend. With time, people are prone to remember the good over the bad. It may also be because some photographers spent years, or decades, working with a particular emulsion, and had their technique completely dialed in. Losing those emulsions was frustrating, and they had to start from scratch with a new film.
~Stone | "...of course, that's just my opinion. I could be wrong."~Dennis Miller