What's going on here? Look at these blocks...

[TheBison]

https://i.imgur.com/ytC5nal.png

Out of the last 7 solved blocks, 3 have been solved by solo miners. Seems improbable but not impossible. Maybe some group is using next-gen prototype hardware and getting really good hash rates?

But look at block 276284 and 276285...

276284's round was 17 minutes long and only contained 67 transactions.
276285's round was 6 minutes long and only contained 27 transactions.

Why are they choosing to include so few transactions?

[BurtW]

All of these blocks were probably solved by pools.  What makes you think they are solo miners?

The number of transactions included in a block is totally up to the miner or pool.  They can include zero transactions if they want to.  Each miner or pool can design their own transaction selection criteria.

For example if it were up to me I would only include transactions that gave me a good fee.  But that is just me.

So, simply put, there were only 67 and 27 transactions at that time that met that miner or pools transaction selection criteria - whatever that selection criteria is.