I believe you meant “in contrast with vertical search like Google”.
I agree in general with your point about incentives. However, there is also another angle to consider: other companies. Google will have to keep innovating to some extent; if it doesn’t, other rival search services may do so threatening Google’s market share (although this threat would probably not be very impactful given the number of people used to Google).
What would you say makes Ommwriter better than Scrivener?