Not at all. Drug dealers have never "given the first hit for free": drugs are expensive, and they're (to a first approximation) lots of fun, they don't need addiction to be sold.
And: how would you even ensure that the person who just scored a free hit will come back to you, and not some other drug dealer (especially if she can just score another free hit for first time customers there)?
However, I think it is a pretty common occurrence that first timers often get their first hit from friends or even co-workers.
