Because you have more than one person you're working with at a time. You get X% of their offer. If they get a higher offer, you get (X+delta)%. If that delta% of the offer that makes up your difference is lower than the value of your time spent doing other things (finding someone else a job), then it doesn't make sense for you to spend the time.
That's the basic issue. If you're getting 5%, then by definition you should care 5% as much as the candidate what the final salary ends up being, and thus care much less if it's a little bit lower than it could have been.
Firstly, our percentage is a lot higher than 5% so we have more invested than you may think.
Secondly, negotiating an offer is the quickest and easiest part. It hardly consumes any time at all by comparison to the amount of time and effort invested just to get to the point where there is any offer at all.
If I've invested a massive amount of time and effort into getting a candidate through the process to the point where the employer wants to make them an offer, believe me, I am going to fight tooth and nail to squeeze every penny from the employer that I can get.
>Secondly, negotiating an offer is the quickest and easiest part. It hardly consumes any time at all by comparison to the amount of time and effort invested just to get to the point where there is any offer at all.
I'll buy that; the recruiters I've worked with have certainly put in a lot of time getting me to the point of having an offer.
The point of serious mismatch is when you're working with more than one recruiter (at different agencies). Some years back, I was almost at the offer stage from company X through recruiter A; recruiter B pushed me to apply at company Y, too. Problem was, X and Y were founded/funded by the same people, and had an agreement (possibly illegal) not to compete on candidates. B somehow convinced me to go ahead anyway; I talked to Y, and X dropped me.
That's the basic issue. If you're getting 5%, then by definition you should care 5% as much as the candidate what the final salary ends up being, and thus care much less if it's a little bit lower than it could have been.