Eggnog And I don't understand why all distro should have a light theme by default... Let's kill diversity and all have the same!
And choosing a dark theme is not only a matter of taste, I do work the whole day in front of screens, and I can tell you that at the end of the day, my eyes are much lesser tired when I use dark themes; I also noticed on my phone (AMOLED screen), the impact on the autonomy is noticeable, when I switch to dark themes wherever I can which is welcome.
The real problem is that dark themes are still poorly integrated/supported and that some dark theme designers don't think enough about people who have poor quality screens (hear most laptop screens) and don't play enough with contrasts to make them comfortable to use.
But that got nothing to do with defaulting a theme. Personally I'm very glad Solus set a dark theme by default with version 4. Of course tastes are personal, but Solus 4 MATE is the best looking out of the box MATE desktop I have ever seen !