Why sign with a small press when I can do everything myself?
You can absolutely do everything yourself. Buying ISBNs, creating cover and interior layouts, organizing signings and events, arranging distribution and printing agreements with domestic and international partners, taking & fulfilling orders, not to mention marketing and all that goes along with that.
Or, you can work with a trusted and respected small press publisher who will handle all of these things for you, and much, much more. The question you should be asking is, do you have the time, energy, and money to do all these things yourself?