Good points. But I'm trying to think of any use case personally where the cover becomes most prominent. 90% of the time I read a book on recommendation of others. When I get burned, and I have several times in book purchases, is when I see a very cool cover, a decent synopsis, and I take a gamble on the unfamiliar author, only to be completely disappointed by the book.
The other time the cover matters is the case you mentioned using Overdrive. Covers have misled me so many times regarding books there that I almost always just check out familiar authors now so as not to waste my time or the library's funds. Truly, book covers are by all means the worst way to choose a book IMO. Recommendations are the best IMO. Better than 70% of the time when I pick books based on the cover it's a terrible disappointment.
Anyone with cash can hire a great graphic designer and have an awesome book cover, but not just anyone can write good or even readable novels
PS--I think because of experiences like mine, that over time more readers will become increasingly wary no matter how shiny the cover of a book may be. What I have begun to do recently is to take a look inside and read enough to get the feel of whether or not I would like the book. That look inside feature at Amazon is priceless, and is becoming my new best friend :-)