Bitcoin client incentives to share peers and blockchain Question a bit related to Microsoft's research on incentives of sharing transactions.

What is the incentive for a custom-tailored Bitcoin client to share information regarding known clients and the existing blockchain? For example, the client could set its "services" in "version" message to 0 and not be bothered with sharing much data. What encourages the Bitcoin clients, asides common curtsey from the people running the software, to share the data?
If data is not shared, Bitcoin won't work. So the people who want Bitcoin to work and be useful share the data. If there aren't enough people who want Bitcoin to work and be useful, then it doesn't matter whether anyone can get the data or not.