I agree, if there is no eye contact saying "hi" is just weird.
But if there is eye contact (especially prolonged eye contact) NOT saying hi is actually even weirder than doing so.
I have an exercise for you...
Instead of just concentrating on saying "hi" to all the beautiful girls, say hi to EVERYONE who have eye contact with you. I don't care what it looks like to you, it will help you break through this barrier.
Another thing you can do is to flirt with ALL women, not just the hot ones. Charm doesn't have an off bottom, so embrace your sexual nature and flirt! Hold seductive eye contact because you are a man! Talk seductively because you are a man! This doesn't mean that you want to take them to bed, it simply means that you are a sexual man who embraces his masculinity.
In my honest opinion, this is how you develop charm and charisma!
I got into it, so sorry for the long post! I hope you could use it

Don't hesitate to contact me if there is anything you want to know more about!
- Andreas