Because they do have a tendency to improve. Jerry Pournelle used to write regularly about his problems with ATI cards in his column on BYTE. They typically followed the same pattern: install new card; install drivers; see computer crash regularly; upgrade drivers; see computer crash less often; upgrade drivers again; see computer run more or less stably.
Then he'd upgrade to the next shiny ATI card and do it all over again, since the new drivers bore little resemblance to the old ones.
I doubt that the mailing list will show any definition of "trampoline". That word has a specific meaning in kernel programming, such that one would already have a good understanding of the subject before poking around in kernel code.
FWIW, "trampoline" refers to generated bits of code containing jumps to arbitrarily different pieces of code, something that ESR called "an incredibly hairy technique" in the Jargon File.
Earth is a beta site.