This is total bullshit.

I live in Köln, and the reason people want to move to Sommerzeit year round is that during Winterzeit near the solstice, the sun rises at 8:30 and sets at 16:30, which means that most people are not getting any daytime sun if they work inside.

They get a tiny bit of sunlight right as they arrive at work, and then when they work all day, step outside and the sun is already gone, which is really depressing. Many many people look at this situation and decide that if they have to choose between light before work or after work, they'd take the light after work.