If we have the Internet, why do people even need guitar lessons?

Well, stuff is free online. A LOT OF STUFF.

But, great teachers and experienced guitarists who teach can help pinpoint things that you might not notice. Things that a YouTube video can't tell you. Of course, I learn tons of stuff from videos and online courses BUT nothing beats being in the same room with a mentor, nothing beats taking Skype Lessons with a great musician (except an in-person lesson!)

It's a different thing. Sometimes you might not need it (or afford it) but those who invest in it, stand to gain a lot!

I personally still invest in lessons with musicians that I admire. Most recently, I attended the Taipei Gypsy Jazz Festival. It was life changing stuff. Learning from Tcha Limberger, Antoine Boyer and Denis Chang was something that I couldn't have gotten online. I feel that so much was transferred from that in-person experience, it made me focus and learn what was important for my practice sessions and gigging life.

In short, if you can, I really recommend lessons with great teachers and great musicians. It seriously helps. :)