Blogging, what is the point: a meta-post

Is the goal of the "blogspot" to be successful or to say what you want?  Technically, it is whatever you want it to be, but why can't it be both?


I was talking to a friend of mine was telling me that to have a successful blog, you have to have a clear focus.  To be successful and to have people read, you had to have a theme and be specialized.  Why?  Who made the rule that someone cannot talk about the diverse subjects they want and still have a blog with readership?


I had wanted to start a blog for a long time but never got around to it still I started to dabble in journalism.  Now, it is something to supplement the work there I do.  So in this sense, I do want readership.  However, I don't see me being able to fit a confined focus.  I am a person with diverse interests from sports to music to law to psychology to any one of several other subjects.  


I wouldn't mind reading a blog where you don't know what to expect week-to-week as a nice change of pace.  Wake up, check the updates, and see what is new on that blog.  I may be biased because thats what my blog is trying to be like and I have diverse interests, but why not?  Half of the "notable" blogs who are specialized aren't even about anything that interesting...like Grilled Cheese.  I like grilled cheese but who can write about grilled cheese 35 times in a year?