I have opinions about this!

Monthly comic book sales have been declining since the golden age. The first big red flag was when they stopped selling them along side magazines and newspapers. The "local comic shop" is fun, but it creates a barrier for entry for non-comic fans. Unlike the past where one could stumble upon a comic at a drug store or gas station, in today's market if you aren't actively seeking out comics you probably won't find them.

Trade paperbacks and graphic novels are the future of comics. When the idea of comic books were concieved, no one thought that people would want to collect or re-read them. They were a novelty to be read and then disgarded like yesterday's newspaper. Today people want to read and re-read their books. They want to collect complete story lines or series, and so it makes sense to update the format to appeal to the modern reader.

Not to mention that trades are a lot more accessable to new readers. A new reader is a lot more pick up an interesting looking trade paperback at a book store than they are to walk into a local comic shop and pick up a random issue of Thor #546.