Spamming comments to the main community and tagging into a log are two different experiences, as far as I'm concerned. Replies to posts are generally done quickly and take little effort. Replies to logs can also be that way, but they are generally ... I don't want to say harder, but they tend to take a little more thought and effort from my own experience. This is my opinion and I'm sure not everyone agrees--but ask yourself why so many people do actionspam in the main community versus posting up a log?

I guarantee that part of the reason is that it's easier/faster/or more convenient.