Should I learn music theory?

Maybe.

 Many musicians don't even know how to read music but still they can make great music, so music theory is optional but it helps.

 You'll learn some theory, indirectly, through years even if it is very basic.

So why should I care about music theory?

 Well, it's a great tool. You basically know every chord and how to create chords. Knowing chord progressions can help you to write songs easier and if you know about scales, you'll write melodies and solos in no time.

 If you study music like me(still studying) you can write songs only with a piece of paper and a pencil pretty amazing if you ask me (sometimes I write songs at work, shhh ;D ).

 You can hit any note with your voice without reference (within your vocal range) and you can find the key of a song instantly.

 All useful skills. 

 Remember: You can still develop all these skills without a formerly study, it may be difficult?, well I haven't tried, so I don't know.

Fun fact:

These musicians barely know music theory:

• Jimmy Hendrix
• John Lennon and Paul McCartney
• Dave Mustaine and Marty Friedman
• Dimebag Darrel
• B.B king
• Eric Clapton
• Van Halen
• James Hetfield and Lars Ulrich
• ...

The list goes on.

  You don't really have to learn music theory in order to play but if do... cool more tools to use. So don't be sad if you don't know everything. What counts is what you play, not what you know.