You're reading the chart wrong. The chart states that the iPhone 3G, released in June 2008, ran the current OS for three years after release, which is correct: the iPhone 3G was updated to iOS 4.2.1, which was released on November 22, 2010, and it continued to run the current major iOS 4.x series until iOS 5 was released in October 2011. (Granted, it stopped receiving updates in March 2011 with iOS 4.3, but that was still the same major version series.)

The iPhone 3GS, meanwhile, will likely get support for at least 4 years, given that Apple is still selling the iPhone 3GS and, historically, provides at least 2 years of support.

As for the Samsung Galaxy, which Galaxy? The Samsung i5500 is pre-loaded with Android v2.1, in the summer of 2011. That's 2 major releases behind!

The Samsung Galaxy S II, meanwhile, was shipped with Android v2.3, which is still the current version (4.0 hasn't shipped yet). It's rumored to be getting ICS, which is good, but previous Samsung phones were also promised to get updates...which never happened. So we'll need to wait-and-see.

Why would Apple want to kill this?

MonoTouch is not significantly different from Unity 3D, which has been used to create over 40 games for iPhone already.

The primary difference is, instead of needing to create user interfaces purely atop GL, you can use the CocoaTouch libraries and get native buttons, frames, html controls, etc.

Microsoft did rebuild Windows from the ground up as a modern operating system. That was Windows NT (as compared with Windows 3.0) back in 1993. Thus, they predated the "let's rebuild the OS from scratch" thing that Apple did by 8 years.

That said, even as a modern operating system, it has a number of anachronisms kept primarily for backward compatibility with legacy 16-bit code, and has even more backward compatibility "hacks" for poorly written 32-bit apps (see the oldnewthing archives -- lots of apps do stupid things), but their priority is keeping existing code working, instead of breaking existing (poorly written) apps. I can't fault them for this.

The only thing removing such anachronisms would do is prevent older programs from working, which really does no one any good (unless you like the thought of Microsoft shooting their own lower-torso off...)