My first job is to replace fluids and belts. After reading my new shop manual and poking around this site, I think I have an idea of how the coolant system ought to be laid out. And... this is not it. Right?

The external thermostat is missing. The lower radiator hose is connected directly to the water pump, and the upper connects to the "tee". The left side of the tee has been plugged.
My question is (and I know it's a dumb one) do I need a thermostat? Without one, coolant will constantly recirculate, right? So, the engine will stay plenty cool, right?
A more mysterious question: Can you think of any reason why someone would do this? Is there an obvious problem the PO was trying to solve by removing the thermostat that I should rule out before I go and buy replacement hoses and thermostat?
I haven't driven it much because I'm nervous about the old timing belt, but when I have the temp gauge was bouncing around 190 the whole time.