there is a lot of reason and its all add into one, from...
- just nerds being nerds
- just because
- could be banned rmt yeah
- someone paid to do so
- could be from se self to attract attention
- its one of the most top mmo out there so naturally it become target
- there is also talk backthen because the spagheti code so the countermeasure is hard to do so (at least compare to other big mmo)

its all come down to "attention", there is reason why old mmo never get ddos anymore