I see... that's the fault of lazy App developers though, I don't think that can be blamed on Apple or OSX. All operating systems change and evolve over time, as we're seeing here with OSX, also with Windows 8 and the changes that brings and I dare say (but without that much knowledge) that Linux variants are the same and also change and evolve over time. It's not up to Apple to re-develop third-party software
If I owned a software house and made software for any OS that I wanted to keep current and on-market, I'd put compatibility with new OS versions near the top of my priority list. In fact, that's why Apple release developer previews like this so early!