Self Publishing has many positives, but there is always another side.
Publishers do a lot for their songwriters in exchange for the rights and 50% of the royalties. They are the ones who collect the royalties from PROs, draft licensing agreements and do all the other grunt work so you can focus on writing your songs. If you do not have a publisher, yes, you get 100% of the money made, but you also have to do all the work.
Publishers are also responsible for promotion. They pitch your song to the radio to get it played and put your song out there to get recorded by artists. If you choose to publish your own songs, then you will have to build a professional network and pitch your songs.
If you get so lucky to get a deal with a publisher, they may offer you an advance in the contract. This is so you have some financial security in the beginning of the contract while you are waiting for royalties to come in. Many songwriters pick up side jobs while they wait to be able to live off of songwriting.
Check out my previous blog to get the pros of self publishing!