Why? Any reason? Better do rapid small updates for faster bugfixes as wait along time for a big update.
Actually no, Rapid Release actually raises the risk of bugs. Bugs were fixed quickly before Mozilla started rapid-release with updates likes such as 3.5.1, 3.5.1.2 for example.
Heres a short list:
Extension/Add-On Compatibility
Lack of new features with big number updates (prime example is in OP post)
Constant updating will interfere with end user
More bugs because of rushed testing
Lack of user knowledge prior to updating
Also, us old Mozilla fanboys of pre v4 that used to get excited for the BIG new firefox version.