Uhhh . . . .no. All manuscripts in the slushpile are eventually read by someone.
But anyone who has ever read slush will tell you – it’s crap. The general rule is 10% is laughably bad and 80% is just plain mediocre – uninteresting characters, recycled plots, weak grammar, cliched use of language, etc. The last 10% is publishable, but may not fit into their needs, or is just not irresistable. Only that last 10% get personal notes.
Now there are certainly some good books in the slush piles, and that’s why publishers still have them (though many are eliminating them, prefering to work through agents; the ease of writing a manuscript on computers seems to have increased the amount or slush). Anything in the slushpile is read by someone.
But readers have no obligation to read the entire manuscript. If it shows nothing in the first chapter (or less), then there’s no reason to read any more. This is not unreasonable: as a reader, if you don’t like the first chapter of a book, you’re not likely to read more of it. And remember, that book you thought was terrible was better than 90% of the slushpile.
I know one first reader who said he could tell if a book was publishable by reading ten pages – that’s enough to get a feel for whether an author knows what he’s doing. (Note that “publishable” does not mean “published” – it merely indicates that the author shows the basic level of writing skills.)
If this sounds unfair, remember one thing: every fiction author you ever read has managed to survive it. Many beginning authors want the bar lowered to accept them instead of working on their writing so that they can clear the bar.