It takes a hell of a lot less mental energy to like something then to dislike it. It's more stressful to swallow something that tastes bad then tastes good or even just non-descript. Stress and expending mental energy hating yourself is really just a great way to be sick all the time and be tapped on energy forever. That's the practical argument.
No person comes out into this world hating themself or feeling like they don't deserve anything. They are told and made to feel that way by others. That's the philosophical argument, that it's not coded into being but learned dysfunctional behavior.
Now... Better question... Why try to like yourself anyway if you don't. You can change as is but... it takes accepting oneself to even begin the process of changing. Without acknowledging what you don't like, that rejected part will never change. Or maybe your criticisms of yourself lack substance or practicality. For me, as I've thought about this for myself before and use myself as an example, I learned the frameworks that made critism of me moot and invalid. I broke the logical basis of critism of me and made it purely emotional through a dose of knowing myself and how the frameworks of relationships and the body function.
