Just for the record, if you're the motivated sort, all the stuff Soccer-Mom just listed is easily done yourself as well. A publisher may do all that for you so you don't have to worry about it, but then they'll also be taking a nice cut of your profit.
I wouldn't call all that stuff 'easy'. It might be easy for
you, but you have skills I don't have. (It also has nothing to do with motivation. I'm highly motivated to do all kinds of things I don't have the skills to do.) That stuff is
really hard for me. I'm perfectly willing to 'share my profits' with a publisher who does those things. Just like I'm perfectly willing to pay a qualified mechanic to work on my car, or a qualified painter to paint my house, or a qualified dentist to perform my dental work, or...
See my point? Everyone is different, and what's easy for one isn't easy for another. A mechanic wouldn't run around telling everyone that it's easy to work on their cars, just because it's easy for her to do so.
These are the questions one needs to examine when deciding whether to self-publish: do I have all the skills and resources (not to mention time) to do all these various tasks? Because if I don't have what's required and try to self-publish, I'm not going to have much -- if any -- success. If someone does have what's required, self-publishing can be a terrific choice.
But what's right for one isn't right for all.