It's not just discourage as you think, it's forbidding in some scenario. If a merchant use a fix address to receive payment , it can only receive 6 payments per hour. Basically makes the service useless. It's customers have to wait forever if there're more than 6 payments per hour.
What merchant uses a static address for all customers? Horribly insecure and prone to problems. Anyone that foolish should just use a service like bitpay and have it done right by someone competent.
See, e.g., the Subway shop in Bratislava, Slovakia mentioned above, and at
http://www.reddit.com/r/Bitcoin/comments/1qrp1h/subway_accepting_bitcoins_in_slovakia_bratislava/ and also the discussion above around non-profits and other entities wishing to conduct transparent finance on the blockchain.