The main reason is that, even when I got proper winter equipment for running in the cold during the last months of winter, I wasn't expecting weather to constantly be under –10° C. That, together with having moved out from Helsinki's downtown and the comfort of having Töölöönlahti around the corner, and having started to regularly swim again, didn't help me to get started training. Probably next year I'll give it a try.
But on the upside, I'm quite happy with what swimming has brought to my life. I never learned to swim properly when I was a kid. In fact, when I was living in Dresden and took a Schwimmen zur Konditionierung class early on Mondays, it was a complete disaster. I could barely cross the 50m swimming pool at Freiberger Platz without feeling like dying and it was hard to keep myself going frequently. I was feeling completely awful and would rather skip it than ridicule myself.
Situation has improved a lot since I started to regularly swim, in September last year. At the beginning, the situation wasn't much better than back in Germany. However (and I think that improved stamina thanks to running was crucial on this), I could do much better this time. By now, I'm doing about 3x500m once or twice a week. I've said goodbye to back pain, I feel way fitter, and all this without any joint pain, which is a pleasure hard to enjoy when running.
Anyway, that doesn't mean that I don't run at all. For instance, on one of my last trips to A Coruña I ran around the city by it's seaside. Really cool place to run.