Because it all depends on your tone of voice and how your advice is perceived. Regardless if you think you're giving constructive criticism, if you come off as a know-it-all or a jerk, people are not going to respond positively to you. Even if you do know more than them. This applies to text and voice coms, so just always be aware of how you sound to others.
I literally just had this situation happen with my guild in WoW. We had a guy with us who knew what he was doing and was pretty knowledgeable with the game, but he was a complete and utter asshole. Everyone put up with him the first week Emerald Nightmare was open in Legion, but once we all figured it out we didn't really need his Holier Than Thou attitude. We told him to calm down and that he was being really abrasive towards others, and when we tried to correct him (he would get lazy in raids and mess up simple mechanics) he would snap at us and call us stupid.
We ended up kicking him because everyone was tired of his attitude. Even though we all know damn well he knew what he was doing, it was his attitude that was off-putting.
So basically, the moral of the story is: Your advice is only as good as your attitude. If you're a dick, you'll get treated like a dick. And not in a sexy way. :P