Is there a minimum number of transactions in a block? What encourages Bitcoin miners to include lots of transactions in blocks in the Bitcoin blockchain?

It seems like you could quickly add a block with just a single transaction and get the block reward from it.

Is there some incentive for miners to include lots of transactions in blocks?
A block may contain only one transaction: the coinbase transaction. However, the time it takes to mine a block is not affected by the number of transactions in that block, so mining blocks with fewer transactions does not benefit the miner. On the other hand, miners collect fees from the transactions they include in a block, so by including more transactions in a block, they may collect more fees.