Everyone who plays WoW has a motivation to play. Usually it is a mix of different things, but there is often times one thing that stands above the rest. It is the main reason you log on and the first thing that you look to do. The great thing about this game is that there are sooooo many diffrent things to do. People who complain about slogging through grinds are not looking at the big picture. Here are some of the motivators for people in WoW (including myself).
Phat Lootz: This one is obvious. Everyone wants those purple pixels. Some people PvP for them, while others Raid and do Heroics for them. Regardless of what anybody says, loot is a large motivator for much of the WoW population. New and powerful items improve your performance and make things easier. Loot is also important for the completionist in all of us. Sometimes, having a single green item amongst all of your purples can be an eyesore. Loot also contributes somewhat to a player's image to the community. People armory you before they let you into anything. They do not care about your skill. In fact, you could be the best player in the world and they will not take you on a raid if they dont think you gear is up to par. Unfortunately, in WoW, sometimes gear is greater than skill.
Seeing Content and overcoming challenges: I grouped these together, because new content usually means new challenges. This is the motivation that many raiders say that they possess. While this is mostly true, it is also used as a cover so that people do not seem like loot whores. Seeing new content that is rich in lore and WoW History is awesome. Beating your head on it for weeks or months is not. New content becomes stale content very quickly for two reasons. You either have it on farm, or you just cannot stay out of the fire. People who want to see new content are not always the same people who want to overcome challenges. I would like to go back and defeat Illidan just so I can say I saw it. It is trivial at this point, but it is ILLIDAN!! Casuals who are into the lore of the game like to see new "content". Many of the hardcore guilds want to overcome challenges, but dont really care about the significance of the content except that it is a spring board to the next challenge.
Social Interaction: Some people play WoW for the social interaction. To me, this is the best part of the game. Finding like minded players who can joke, have a good time, and maybe kick some ass. An MMO without social interaction is called Baldur's Gate :) There are different kinds of social players in the game. These can be the people who play with the same friends all of the time. Trade chat and forum trolls also fall into this category (real trolls, not gold spammers). They want to log on and use WoW as a glorified chat room with a mini game on the side. There is a trade chat troll on my server who is only level 73, but is online ALL THE TIME. It is hard to be a social troll when you are out questing or doing dungeons. Social Interaction is in almost every aspect of WoW. You can solo all you want, but if you want to obtain top line loot and see new content, it is pretty much impossible to do solo.
Collecting and Achievements: To some players, the end game is not spelled PvP or RAID. There are plenty of people out there that are content to tick off some achivement boxes and collect things such as vanity pets and mounts. To these people, doing a Holliday Achievement is much more fun than killing Malygos. While achivements are the new phenomenon in WoW, collectors have been around forever. These were the people who filled their bank slots and bags with vanity pets before they were used like a summon spell. Collector does not always mean casual. Many collectors keep bank bags full of the phat loot they earned from what was once the cutting edge of raiding.
There are many, many reasons why people play this game. I fall into every single category above. If you are playing for any of those reasons, you may be doing it wrong. The real reason you should play is.......
TO HAVE FUN AND RELAX: Regardless of anything I have said above, WoW is a video game. It should be fun for you. Do you go to the movies and get stressed out over how dumb the main character is? If you get back to having fun, the game is a million times better. You will enjoy your time. People who have the time, but only log on for raids and then log off immediately afterwards are missing some of the best parts of the game, not to mention treating it as a job. If you find yourself dreading logging into the game that you once loved so much, it is time that you take a step back. Look at the cause of that frustration and eliminated it. IT IS ABOUT YOU. If Raiding and drama in guild is frustrating you, just g-quit. Do your own thing or find somewhere where you will be in an enjoyable atmosphere. We only live once, and if you are wasting it on a hobby you hate, you will regret it down the line.