Traffic has no impact on your SERP visibility. It won't improve it, so doing this will have zero benefit.
In fact, it could even be hurting them (at a stretch). What are they doing once they click through? If they're bouncing off and not spending time on the site, that could actually hurt them. Bounce rate, to some degree, is taken into consideration when Google ranks your site. It would take an awful lot of bounces, but if Google sees people coming to the site and leaving quickly, it's going to start to think "this page does not serve the user".
I wouldn't worry much over clients doing it, but I always believe it's important that clients should understand the basics of SEO, so that they can appreciate your work but also for transparency's sake in the line of business. Educating them over this (and probably personalised search, by the sounds of it) would be a start.