There's a limit to what recruiters can do. In general, good recruiters have been incredibly helpful to me in understanding exactly what opportunity they are looking to fill, to match expectations etc. But after a certain point, its gotta be a conversation between the applicant and the company and that is something that recruiters can't affect much.
I agree - it's about focus and time. Recruiting is already a very manual process, and it's hard enough for most recruiters to identify candidates and get them interested in the role. The conversion rate from initial outreach to interested candidate is abysmal. Adding a layer of advising / resume help just doesn't fit with their model and would make them uncompetitive with other recruiters.
At HireArt we certainly do try to do this, but we're still a small part of the recruiting market.