editors, working for publishers, are behind a lot of the great literary works of the united states.
True, but publishers have been giving authors less and less editorial support as the continue to cut costs. The theory is that the slush pile is so deep that, if they dig enough, they can find a manuscript that doesn't need significant editing. Or they wait until a new author has some proven success before investing in editorial assistance to take him or her to the next level.
publishers also deal with libel and defamation lawsuits for you.
Possibly true. Most contracts I've seen say that the writer is ultimately responsible. Even so, in fiction (which is what Barry Eisler writes), there really aren't that many suits. Independent authors can incorporate to shield their personal finances from their professional writing liabilities.
they also set up junkets so you can market your book.
For fiction, this is extremely rare and of limited impact. If you're a big seller, then you might get some co-op promotion (placement in end caps and feature tables in the bookstores). Publishers will sometimes circulate advance reading copies to generate reviews. Most new and mid-list authors have to do a ton of self promotion, mostly at their own expense.
im not saying theres no point to self publish, but there are many differences between music industry and book industry.
It seems everything you've claimed about the publishing industry could also be said about the music labels. What's the difference you're trying to highlight?