It was definitely odd when Ryanair acquired this 737-700 (reg EI-SEV).
Firstly, it is already 17 years old, making it the oldest in Ryanair's fleet. For an airline that has just been buying plenty of brand new planes, going second hand seems strange.
The type difference was also noted. There were suggestions that a 737-700 is cheaper to fly for training purposes than a 737-800.
It seems this plane makes one or two return journeys each week, so sits idle most of the time.