to do tasks faster than a human being, giving them an unfair advantage
[not exact words]
Now, Jagex should think : why ? Why do people enjoy doing skills faster than they normally should be able to ? Simply because :
1) They are long, boring, there is NOTHING fun about running from the bank, click on trees until you got an inventory full, run back to the bank and continue.
2) They take much too long time, a human being in general has, lets say, 5 hours play time on a computer game like runescape a day ? And he gets what ? 50K exp / hour in that skill which he levels while playing ? In other words, 250K exp per day, you need approximately 54 days, of non stop leveling for 5 hours a day to get a stat to 99.
Botting is more convenient as you can spend your time doing something fun meanwhile instead (or useful [botting during work for example]), Runescape's only fun aspects, imo are the PvP aspects, all the others are endless cycles of repetition.