Don't want to spend too much money as I re-accumulate funds (thanks, job!), so I'm not going shopping or out to eat at the moment; I'm in the mood for a quiet day, and that's easier to have at home; I have cat access, plus the cat here likes me; Twitter's providing me news from the madness that is San Diego ComiCon, so I can get cool news without braving being among 130,000 people in a convention center to get it; I have food close by.
Another reason: I want to have my bedroom window open for a while, following our stretch of 90-plus degree days that were even a little humid. Not Southern/Midwestern humid, or even the Virginia level of humid that once was enough to make me feel ill; but yeah, a few days ago Portland was humid. Now that we're cooler and drier, I want to air out the room. And one of the rules in this house is "don't leave first-story windows* open when you leave, because there won't necessarily be anyone in the house to make sure it's safe to keep a window open." So, stay put, enjoy a slight breeze, and relax in my place. I CAN DO THAT.
* Presumably this applies to the basement windows, too, but I mostly go down there to do laundry so this doesn't affect me. There. Bases covered.