Resource Credits are technically has the same concept with Bandwidth. However there were some technicalities which Resource Credit offers a great solution than Bandwidth. One important is calculating the "true cost" of the transaction. Cost of a transaction varies depending what did you performed on the Steem blockchain. Currently, Bandwidth only consider the size of the transaction, which technically is flawed and the main reason why spam accounts and bots exists so much in the blockchain.
The current account creation costs 0.1 Steem and 14 SP Delegation. Steemit Inc. has used more than 6 million Delegated SP to create accounts per user. Which will be very costly for them, which is the reason why we have low account signups. Instead, 0.1 Steem and 14 SP delegation will be changed to using user's Resource Credits to create accounts.
Why isn't Steemit trying to remove all the bots? I feel so frustrated and irritated when I get to know that someone commented in my post and after viewing it, it is to be a bot. All my excitement of making people attracted to my post turns into frustration and sadness with some sparkle of anger. I think Steemit should focus more on this than any other thing, Right now!
The truth is it is completely decentralized. We cannot stop what other people wants to do. Nobody can.
That's why they're building things that discourages the things that you mentioned above ( and more than that ).