There is the obvious reason, posts in which I respond to other things, or even develop my own idea seriously, tend to be longer, and thus take more time. They need to introduce whatever it is I am referring to, in a way so that the people who don't love hyperlinking around the Internet discovering new, interesting, and awesome things will have an idea what I am talking about without reading the source link.
It also is a more arduous process because I feel the need to give weighty consideration to what I say. In this post, after I decided what I wanted to say and why/how I would say it, I basically am just writing as it comes to me. But if I am developing an idea I think is important/interesting, or, to put it another way, about which I would really like some discussion and constructive feedback, I feel that I should take the time to structure my thought in an interesting, appealing, and accessible manner, which takes time.
Additionally, if I am responding to something thought provoking, I feel the pressure to make my response a worthy one. If I don't add meaningful thought to the discussion, then I might as well have just posted the link and let you simply read it for yourself. So, while response posts are quite interesting to write, as you might guess from the number of them I do, and pleasant in that I don't need to worry about coming up with something to talk about, they do require a lot of energy.
I don't have a lot of energy, so you got this today ;)