Where did you get that email from? I'm pretty sure Ryanair dont even use email with respect to customer service.
They do but it's pretty rare. I received a questionnaire from them back in 2005 but haven't had one since (despite having booked maybe 80 to 90 flights in the meantime).
It's the cheapest form of market research. All done in-house as far as I can tell to do away with the need to contract expensive external consultants. Classic Ryanair!