I think it might have something to do with the explosion of homelessness in Seattle over the last few years. When I moved to Seattle ten years ago that library was amazing, and open pretty late (I think 8 pm). But last time I went there like a year ago it was completely overrun with homeless people. They were everywhere in the library, just sitting around doing nothing (not reading or using computers), and dozens of them were outside of every entrance too. So, I think they might have adjusted the hours because of that, instead of directly dealing with the problem. I don't really have an issue with homeless people taking advantage of a public resource, that's why it's there, but a lot of other people do, and the city has to consider everyone's perspective.