Which sadly includes me these days, since it's such a pain to run multiple versions of Firefox and there are legacy extensions I can't do without for some things.
I interpreted the comment to mean, they run old FF (with extensions) alongside chrome (incompatible), because they don't want to run two versions of FF. I don't quite understand this either, but it makes more sense than the other interpretation, I think.
Bingo. DownThemAll is something I would describe as "mission-critical". I had trouble getting two different versions of Firefox to not interfere with one another in odd ways such as everything running fine until I open a file with Firefox as the associated program and one version would open but have all the settings from the other version and Portable Firefox refusing to save settings or extensions at all. Using Chrome for casual browsing was just less of a headache.
>I had trouble getting two different versions of Firefox to not interfere with one another
This shouldn't be an issue if you run your secondary instance with -no-remote -profile="your separate profile".
>Using Chrome for casual browsing was just less of a headache.
That still doesn't answer the original question though. Why choose chrome over firefox, when it has no legacy firefox extensions? Does chrome have those legacy extensions' features built in? Was chrome better than firefox, and the only thing keeping you on was the legacy extensions?