I wonder if this is true of self-published, ebook-first writers. In conversations with agents about my novels, I was told that they needed to be "longer" and that ~70K words wasn't enough or wasn't sufficiently "commercial." But in my view the novels were the appropriate length to the material (see
http://jakeseliger.com/my-novels/ if you're curious). With ebooks, I don't think readers are subconsciously swayed by length as they are by physical books in bookstores.
Indie authors also often point out that they're better off splitting one massive tome into multiple parts. A novel like Neal Stephenson's Seveneves might've been split into three to five parts, with the first one given away and each additional part $.99 – $2.99 in its ebook edition.
EDIT: Also, I'm not opposed to being commercial, and indeed if I could think of more / better ways to be more "commercial" I'd do it!