I am currently looking for a job and after almost every interview I get a question If I am invloved in other recruitment processes and then I get a request of notifying the recruiter in case of positive result. I always respond 'of course' but I don't feel like it at all. I have no interest in doing this. I feel like they want use me for making their job easier. I feel like they want me doing them a favor.
I don't see what issue you have with it. Yes, there is some sense in which it makes their job 'easier", but it so in a way that aligns with your interests; the reason they want to know presumably is so that they can have a chance to outbid whatever other offer you got. If you're concerned about having to keep track of all the companies that have made this request, you can give a response along the lines of: "I'm currently looking at a large number of companies, and will be unable to keep them all informed of the status of my application at the others, so I'm afraid that I will have to limit this sort of appraisal to companies that have given me a firm offer". This will reduce the number of companies to keep track of and give the companies a further incentive to give you an offer.
why do they ask you to keep them informed of any offers received?:
They might be able to use it to speed the hiring process along. They can tell the people making decisions that if they don't hurry they might lose good candidates.
They might might be able to speed up the process of getting you an offer.
They can use it to eliminate you from consideration. Especially if you tell them that you accepted an offer. This saves them time.
They get an understanding of their competitors.
The second one is the only one that helps you the applicant. Though if other candidates keep the recruiter informed the 1st and 3rd reasons could help you.
Remember the recruiter doesn't work for you. They work directly for the company with the opening, or they have a contract with that company.
You don't have to keep them informed. You don't have to reach out to them. If they contact you for an update after you have accepted an offer with no contingencies, you can inform them then.
The only reason to tell them about an offer is if you want to have your application for their opening move along faster.