I don't know, I think he was trying to get the price down because why pay more than you have to?
Also, I think a decade's-worth of notable human discourse in discreet packets of n-characters in an already hierarchical organization paired with deep demographic metadata could be seriously valuable.
Lawsuit protection and the pairing of tweet data with internal demographics data? There's no telling what Twitter knows about its users from being installed on their phones(geocoding, network analyzation, etc.) to analyzing their advertisement engagement to sentiment analysis of word choice and it goes on and on.
As stupid simple as the tweeting/re-tweeting mechanisms are, that doesn't mean they don't have serious targeted marketing algorithms and other high end data analysis tools behind the scenes. It would be silly if they didn't.