1. Kills RSS - forces people to receive updates from people / blogs / companies you want to follow in email.
2. Wow, that inbox is looking pretty messy - we should help clean it up!
3. We made a nifty little app to help keep your inbox clean (and filter out those annoying companies you used to subscribe to via RSS).
4. Our customers like their inboxes clean - so if you're a company and you want to talk to your customer - you better pay for a spot.
RSS + Email were dumb pipes. Google's doing everything in it's power to control those pipes either y eliminating them (RSS) or using their near-monopoly to shift people to a new standard (gmail/inbox). Now, this is all smart on their part, but not necessarily great down the road for consumer or companies.
This smells like the "new coke" argument to me.