Blockchain - Incentives to Miners
A miner may be overwhelmed by transactions at any given time, since the maximum block size is predetermined in the system, requiring that only a certain number of transactions be included in a block.
Depending on the block size and the average length of each block, the number of transactions in a block varies. It is important that the sender does not include too much information in the message so that it is short and incentivizing the miner to accept it before the other lengthy ones.
Senders often add a transaction fee in terms of bitcoins to incentivize miners to include their blocks early.
Another consequence of building the blockchain is its sheer size. Over a period of time, the entire blockchain may become too large for a node to store on its disk. This issue is resolved with Merkle Trees.