Then please, why write 800 pages when everything can be covered just as well inside if not 300 then 500?
It can not be because the author thinks the story is any better for it, the padding is often far too obvious and some have subsequently condensed their books for use as radio readings, 90%+ words lost without the story disappearing!
That's a good question. And there are several answers to it. First, it is important to realize that this is a money issue for most authors. Not that they get paid more by the page (that is only for short stories in paying magazines), but often the bigger the book the higher the retail price. Plus, there is always the hope a big book will be issued as a trade paperback, and that is a big jump in price from a mass market book, meaning more money for the publisher, agent, and author. So this is one reason why many agents and publishers push their authors to write long...more money for them in sales and commissions! Also readers tend to think a big book is a "good" book, meaning better story and better quality writing. It makes no sense, but it has been this way for the 30+ years I have been in the book business, and it doesn't look like it is going to change any time soon. Also some authors tend to write long naturally. Some are good at it, and some could use a ruthless editor.
I do agree with you, and that is because padding bores me too as a reader (and as a writer). It reminds me of Danielle Steel (wrong genre, but good example). If you have ever read one of her novels you can see she has a formula for her books that allows her to stretch out the length. This formula includes 2-3 page descriptions of every outfit the main characters wear (including most of the minor characters) EVERY TIME THEY CHANGE CLOTHES. That takes up a lot of space in a novel. It also makes it possible for her to write 2 or more novels every year, and her fans love it. I never understand it, but they do. Go figure. Now she may have changed, because I haven't read one of her novels in over 10 years (I had a friend who just raved about them, so I tried a few...but not my thing).
So I agree with you...I think you can have too many subplots going on in a novel. That often tells me the book should be two novels or a series, but not one big confusing mess. Another thing that drives me nuts is a big novel with lots of characters, and 3 or 4 have similiar first names, meaning names that begin with the same letter or letters. Now that is hard to follow, at least for me! I know Shakespeare did it, but at least with a play there is a list of characters at the beginning, so you can mark that page and keep going back to it when you get lost in all the similar names.
Tight writing is a beautiful thing to behold. I wish there was more of it. But then many books would be very slim, and the big publishers are having a hard enough time making ends meet this year as it is.