Because everyone and their dog would say they want it, or are interested in it, even if they don't actually want it. This puts up a (small) barrier that helps g

Because everyone and their dog would say they want it, or are interested in it, even if they don't actually want it. This puts up a (small) barrier that helps gauge true interest. It's the same idea as setting up a landing page for a product that doesn't exist and seeing if people click "pricing" or "buy now" to determine if there is a market for it.