As a matter of principal I always ask for Crystals and Clusters up front. If they are not forthcoming with said catalysts, I return their items to them and tell them to find somebody else to craft for them. Most of the time they accept it but you do get a few people who get quite vocal about how they are entitled to use your crafting skills.

I would suggest on the occasion you meet these people you tell them where to put it, because people like that deserve it. Don't generalise though. The majority of people I've crafted for always provide the Crystals and usually thank me for my time, usually in the form of a tip. As always, a few bad apples spoil it for everyone else. Don't be fooled. There are {generally speaking} more people who actually appreciate crafters than don't.