I suspect that authors, most of whom tend to be artists, would be a bit less than adept at the mechanics of detail-oriented proofreading. Those of us who are not artists or who are not involved in getting the ideas down in print, would tend to be better at catching the odd misspelling or format error.
Having said that, I have read texts from both 'big name' publishing houses and eBook indies that contain errors that should have been caught by any word-processor spell-check program (i.e. 'ou' for 'you'). This is just plain inexcusable in today's world of instant spell check and thesaurus editors. Even though many electronic editors cannot handle 'properly spelled' context errors (to, two, too), the simple stuff should never survive.
If authors are simply throwing text on a page without any proofing whatsoever, then their work won't hold up long in the public sector, unless of course, the same shoddy products are being allowed by the big-money publishers who are short-cutting product quality for profits. There are times when the lowest common denominator should not the be benchmark.
On the other hand, is a properly formatted, spell-checked book necessarily better than one with a few editing errors that is nevertheless devoid of content? And is it worth a $35 hardcover price as opposed to a $3 eBook offering? I guess we'll find out.