The title means nothing. If you claim "senior" on your resume, a prudent prospective employer will have you back up your claim through clearing technical interview hurdles, showing code samples(*) and describing some of the challenges that you took on. And make its own determination from there as to your capabilities.
My best guess is that recruiters don't really care about titles but they do care about the salary they can negotiate on your behalf because their commission is pro-rated on that salary. And of course, they can negotiate a better salary if they can point to either something you did or something you can do that matters to the client. Recruiters don't get paid extra simply because you have "senior" next to your name.
(*) Konerak points out that not everyone is a developer. If this is not the case, prospective employers will think of something else than code samples like "tell me of a tough issue you encountered and how you resolved it"