Well. Some of them are inconsiderate, and then if you’re a girl, they probably don’t have an idea how to read you. Basically, they’re confusing because they can’t understand you…and some of them are too inconsiderate to take time out of their day and figure you out.
For instance: generally, when you say hi to someone as a girl, you also communicate through your body language. You might smirk or frown at them if you’re mad, grin really big if you’re happy, and not only that—-typically you’re also analyzing how THEY are looking at you when you say hi. When most guys say hi…they are literally JUST saying hi. No analysis, not a lot of body language.
Guys and girls are very different. We communicate in different ways. But, THIS IS NOT TRUE FOR EVERY GUY AND EVERY GIRL, just to be clear, and not all guys are inconsiderate, just to be clear.
I hope I helped a bit. There are other reasons that guys can be confusing…but the list is much too long to go through. The best advice I can give is DON’T read too far into their body language. Read more into what they say to you and how they say it.