Big youtubrs have actually started using them. I think they do make videos look more cleaner and they also leave a lasting impression. For instance FreddieW Puts his Rocket Jump logo on his vids now. Not only does it look better but it also directs traffic to his website. Tobuscus has his name on the intro and his voice. Its catchy and memorable so if it gets stuck in your head everytime you get on youtube you may go to his channel more often because of it. Other youtubers have catch phrases as openings Destorm "Whats up world?" Toby games "hello once again audience" Philip DeFranco actually has a visual intro and a phrase " Sup Nation?"... It depends on how you brand your channel. anyone can have a intro no matter what kind of videos you have. You just have to see what kind would make sense to your audience.
 
Now with that being said there is a not so good way of doing intros. A example of this is BachelorsPadTv he has awesome skectches they get like 100 thousand views easy But there is a problem. He has only 17,000 Subs. I say its a problem because he is only converting like 6% of the viewers into subscribers. He used to have 49 second intros to a 2 min sketch. You see him drive up in a lambo to a mansion in a robe whith his name on the back King Bach you got females on both sides of him and runnin around through the mansion in lingerie while his theme music is playing and it ends on his logo. First how can anyone relate to this not that many people have lambos a mansion or that many women running around half naked unless you are Hugh Hefner. Then when thats over he opens with another intro before you even get to the actual comedy. Now hes on a couch with more half naked women and hes talking about the video hes about to show for another 40 sec and telling the the women to shutup when they talk. So now you just lost most of the female viewers because of that. I left the comment before on a video now I dont really see him using this intro that much anymore. Sorry I got long winded But long story short intros and outros are good if used effectivly to get people to subscribe or push traffic to your site.