When a smart small company hires a recruiter, part of the goal is to have recruits never really realize they're talking to recruiters. Presumably most YC recruiters aren't randomly cold calling people; instead their job might involve a lot more of "setting up circumstances so that the right person in their company is likely to end up talking to Colin Percival".
Most of the time, when people complain about recruiters, they're complaining about dialing-for-dollars cold-call transactional recruiters.
Recruiting is a special form of sales/marketing, and most businesses wouldn't expect randomly calling people on the phone to be their best early sales strategy. But that doesn't mean they don't do sales; they just execute on an early sales strategy.
Jeff Cox's _Selling The Wheel_ is a good, if somewhat patronizing, summary of the different sales strategies companies use at different stages of the adoption curve for their offerings. The same insight applies to recruiting.
