Nostalgia, the vice of the aged. We watch so many old movies our memories come in monochrome.
The skills that we have are the actual magic skills - not the performing skills. We have to separate those. But the actual skills that make the tricks work, we don't get to use again.
In some cases we've been building tools that are specific to Linux for the desktop, and they only work on Linux, but I see two major projects that are wildly, wildly successful: Mozilla and OpenOffice, and those two programs are cross platform.