It's a really good thing Steem has many keys. It makes the use of Steem much more secure. You have four pairs of keys each made up of a public key and a private key.
With this key you can function in all of your roles: post to the blockchain, open private memos encrypted with your public memo key, transfer funds, power up, power down, use the internal exchange etc., and most importantly, change all of your keys. Keeping your master key safe and offline as much as possible is very important!
With this key you can transfer money and use the internal market.
With this key you can make posts and comments, edit and delete them, and vote.
With this key you can read memos (text fields attached to transfers to you) encrypted by another user with your public memo key. The memo keys enable you to have confidential communication with other users.
Using just one key, your master key, everywhere would put your account and all your hard-earned funds in danger.
Well, different keys have different functions.
E.g. posting keys for posting and voting on the blockchain, active keys to make transfer, owner keys to validate ownership and memo keys to facilitate memo sending and reading.
It's actually a great idea because there would not be a single key to control all functionalities. As such, in cases where the keys are compromised, let's say the posting keys, you would still be able to gain access to your Steemit account!
The keys actually have their functions! So, better know them well and always choose to reveal the necessary keys only!
Because it is integrated with blockchain, making all systems safer, keep away from hackers, because it is encrypted.
each keys on steemit has their own functions,i believe all these keys is just a good way to secure your account and make it very difficult for anyone to steal money from your steemit wallet,though some users could find it incovenient to be entering different keys whenever they want to use some certain features on steemit,but i believe that it is bettee to be a bit inconvenient than to loose all the money in your steem wallet....