Not only do quests give you great amounts of EXP, but many quests also give you reputation. As you earn more reputation, higher quality rewards become available.
Quests also give you valuable and free equipment. Earning your equipment through questing can save you copious amounts of time and money.
Cultivation Quests are required for any player to complete if they do want to learn new skills. Each skill requires that you have a certain 'cultivation'. Higher cultivation levels also reduce the EXP penalty from dying.
All cultivation quests start at level 9 and end in 10 levels. They then restart at the next level set (9, 19, 29, 39 etc.). There are a total of 9 sets of cultivation quests which you must take in order to obtain every skill for your class. This section lists 7 because the level 9, and 19 Cultivation Quests are found under the Race Tab, these are the 7 cultivation levels in which 'all' characters do the same quests.