Ideas once rejected can still be re-examined. Innovations left half way can still be successfully accomplished.Even scrap unfinished IP can be very useful component of a really innovative IP. An idea that could not be proved at a given point of time or by one individual or by one institution at a time and left half way ,due to lack of further investment ,man power ,infrastructure can be continued after a break by some other individual or institution and can be successfully completed after further investment.
Scrap IP are also subject matter of IP world.
Deal with it effectively. If necessary,deal it through law. Make provisions. Law also has to be innovative ,forward looking. Stagnation stinks.