There really isn't any incentive to include transactions in blocks.
There are transaction fees.
The miners have an incentive to maximize their immediate revenue because their equipment has a limited useful life.
Including an additional transaction into a block does have a cost because the miner needs to validate the transaction is valid, and for each additional transaction included in a block, it will take an incremental additional amount of time for the block to get propagated to the rest of the network.
Based on orphan rates of under 1%, and according to BlackHatCoiner above, a ~1.7% rate of total block rewards being made up of transaction fees, the theoretical maximum cost to include any transactions is below the revenue generated by including transactions. As such, including transactions is EV positive.
It is difficult to know with certainty if the timestamps of the block in question and the prior block are accurate. Timestamps can be up to two hours off and blocks will still be accepted.
To answer the OP's question, for whatever reason, the miner that found the block in question, ViaBTC, was unable to construct a block that includes transactions after they received and validated the prior block, prior to them finding the block they found.