There really isn't any incentive to include transactions in blocks.
That sounds incorrect, pal. 
It's a modest amount of processing power required to test, pick and commit transactions to block (nearly a quarter of the bitcoin codebase is dedicated to this).
Creating merkle trees does require a little bit more of the processing power, but there's no way this will disincentivize the miners if they're going to get an extra fraction of a bitcoin, just because the block subsidy is greater than that.You could argue that the fees are the incentive to include them in a block, but when you are talking 6.25BTC ($184,000 USD) as the base - some aren't bothered by this.
In the last 10 blocks, the average income from fees, alone, is 0.107 BTC. That's 1.712% of the block reward. I would bother to earn it, even with higher chance to be beaten by propagation, even if I had to compute merkle trees.Another possibility is the stratum/pool mining software responsible for this block is not connected to a full node, rather a lite or SPV node. To build a valid block, you really only need to know the previous block hash, the height and the coinbase reward. Running a bitcoin node again, is quite resource intensive - and the disk space alone is 405Gb (standard, not txindex) - I can fully see a situation where some clever software simply listening to the headers could work.
But, running a full node is a necessity if you want to be accurate and sure. Listening to an SPV node increases your chances to be beaten in propagation as you receive the info later than the others.