Re: Windows 10 did especially well
i can think of a lot of software which worked in OS x 10.8 and died on impact with 10.9. The vast majority of it was software which went out over the network, including email, ftp, and usenet systems, and all of them used a technology named 'Open Transport'. Apple had 'depreciated' Open Transport when the very first OS X versions hit the street. Developers had been on notice for years, since OS X 10.4 in 2004 or so, that it was going to go sometime. Not only did they not migrate to APIs which were going to be supported, some rolled out new versions of their software, using the old APIs, a few months prior to 10.9 hitting the streets. Others simply hadn't updated their stuff for years. When 10.9 hit, there was much wailing and gnashing of teeth... tough. It had been marked as being doomed years before, and the devs had not paid attention. Open Transport had been around since 1995. It was visibly growing moss.
In the case of 10.6, a lot of the dead software depended on having the old Motorola 68000 APIs around, and some depended on PPC APIs. By the time 10.6 arrived, there hadn't been new 68000 Macs for well over a decade, and there hadn't been new PPC Macs for several years. And Apple had told everyone who was listening that the old stuff was doomed. The only thing they didn't say was when. Turned out it was 2009. That would be three years after Apple started shipping Intel Macs. Devs had three years to move on. Whose fault is it that they didn't, again?
I personally have an old eMac sitting around just so that I can play a very old game (Harpoon; I love sending in regimental Backfire strikes against imperialist carrier battle groups or flushing all the Shipwrecks, including the nukes, from an Oscar at very close range to a Yankee carrier... Slavsya, Otechestvo nashe svobodnoye! Nothing like 54 to 81 Kingfish or 24 Shipwrecks to ruin an imperialist admiral's whole day! The Glorious Red Banner Northern Fleet owns the Atlantic!) and I'd just love to be able to play it on modern equipment, but the vendor's dead and it will never be updated.