Chrome has always maintained a stable extension API, and have largely stuck with it (I'm not aware of any deviations, but I don't discount the possibility that they've existed.) Also, because they never exposed a version number in a prominent way, we haven't had web developers targeting versions of Chrome.
Firefox maintained a stable extension API, but then they also hosted third-party extensions which used unstable interfaces. By hosting them, they gave legitimacy to the unstable interfaces. With every Firefox version update, a handful of my extensions would break. When they first started the accelerated versioning, it was horrible. Now things have stabilized a bit, so there's that. Additionally, I spread my annoyance to both Mozilla and to Web devs when there's a "target" version of Firefox and later versions won't work with a website. For the web devs, "Dammit, write to the standard!" For Moz, why are they changing their rendering engine so much that it breaks compatibility with existing webpages?
But mostly, I think people just gripe at change. They didn't (seem) to complain that Chrome doesn't prominently display the version number, but they balk when Firefox decides to start doing that. Some of that may have been because of the issues related to versioning in the past--I don't know.