Some creative types don't need a guitar teacher
I have a friend who is a free-spirited creative type. She lives her own creative life, works whenever she pleases (though at times she's broke), and freely plays music in her own way. I am a bit jealous of her because she does the same with guitar. She just doesn't care about what anyone else thinks about how she plays. She doesn't know how to play any songs; Songs don't interest her. Just the mere fact that she is playing guitar and making music her own way makes her happy. She is a free spirit.
If you know yourself well-enough to say that you are like my friend, a free spirit that just likes to create music on your own without any need for external input or validation, than take it from me: Don't feel guilty about not taking guitar lessons.
Frustration is a sign that you need lessons
Creative spirits like my friend above are relatively rare. Most of us, myself included, are the types of people that do well with structure. Are you the same? Do you need a little direction and structure to your learning? One way to tell is if you feel frustrated learning guitar on your own. If this is the case, then my suggestion is to start looking for a teacher, and soon.
Guitar teachers can optionally provide us with a shortcut to learning guitar. Teachers can help us achieve our goals a little faster, especially if you are the goal-oriented type of person. If you feel frustrated learning guitar on your own, take my word for it: It's time to find a teacher. They'll help get you there faster.