HK Headhunter's "after sales" service

Talking about the importance of after sales service, I suddenly think of how headhunters in HK provide the "after sales services" to their customers and also to their candidates.

Usually, after placement, if the candidate left the company within 6 months, the headhunter is obligated to place another new candidate for free. However, recruitment agents would also collect feedback from candidates to see if they are satisfied with the new environment. If the response is negative, they will recommend you another job. It is, however, there's an implicit prerequisite for this service. That is, you have to make use of your probation period (6 months) to find out how the new job is unsuitable to you. In other words, they have to make sure they will perform their after-sales service to the candidates only after they get the commission from their clients! How evil it is!