Why isn't Chromium up-to-date in all the Ubuntu LTS repos, like Firefox is?

Firefox is in main, and Canonical commits to providing security updates for software in main (which, in the case of a browser, is all of them). Chromium isn't in main, it is universe - so it is updated by volunteers. It might have simply become too much of an effort to update Chromium for 12.04, all the more so since Google doesn't support 12.04 for Google Chrome, so breaking changes might have been made since.

For 14.04, the latest versions of Chromium have failed to build, bugs have been filed with no response from maintainers. Since Chrome still supports 14.04, I assume this might be fixable, and no one has volunteered to fix it.

I know a little of this.

Beyond chromium not in main and hot having a guaranteed support policy, there are a few other reasons older versions can lag or be unsupported.

lang C++: 12.04 was released around the time that a new C++ standard was developed, and Chromium upstream soon thereafter adopted the new language features. The 12.04 system c++ runtime doesn't support them. It is possible to use build tools that were never in 12.04 and retro-fit ABI changes, but it's kind of hard. Static linking like proprietary Google Chrome isn't very good. Non-main and very old distro made this lowest priority.

arch x86: Upstream chromium dropped i386 support. Ubuntu still must support it. Firefox doesn't have this extra burden.

arch arm64: We wish to support new desktop architectures in Ubuntu, and while there are mobile phones running Chrom-e, ARM64 desktop isn't even on Chromium upstream's radar. Firefox upstream has better support.

velocity: There are fifty something major-version releases in a relatively short lifespan of project. Add that insane pace to the above troubles and and some other more minor things like next month's gtk2->gtk3 replacement, and all make chromium unusually hard to support, or harder than Firefox is.

If there are volunteers who wish to help, then I want to help you to help. Join Freenode #ubuntu-chromium . Your task is to clone the "working" packaging branches and propose merges. https://code.launchpad.net/~chromium-team

Thanks!