That is actually a pretty good question and I think it is very important to answer that one. Back at the beginning of Steemit and the Steem Blockchain it was essential for the developers to build in a tool to help burning Steem. If we look at this from an economic point of view, through upvotes Steem is to be generated but not destroyed. Therefore more and more Steem will be available on the market. The price of Steem results from the meeting of demand and supply of Steem. If you think logically, you will quickly notice that there will always be more supply then demand and therefore the price will not increase. So in order to solve this problem, Steemit invented the function called "Burning". There are mainly two ways how you can achieve this: One way could be to send Steem to @null which will result to a destruction of the Steem burnt. Every normal person won't do this for the sake of the economic balance. However, there is a second function build in called the promoting tab. However, the sad truth is that nearly no one is using it and no one is looking under the promoted category causing a permament imbalance of the ecosystem.
Hope this helps. Let me know if you have any further questions.
It helped, yes, but I didn't even noticed the promote button. I will look more into it to see what it does and how Steem gets removed from the blockchain by promoting.