i believe this trend is a result of management culture and performance metrics that attempt to measure "impact", and correlate pay and promotions along those measures.
It's the same reason why google products die when they don't reach mega-success (thus products getting killed off in spades recently).
Nobody wants to be doing maintenance on projects started by somebody else - so as soon as the lead visionary leaves for better pastures, that project gets languished, and whoever takes over it cannot use it to generate promotion worthy impact.