Because people are anxious to finish 1k so they can get their hats,but then are to busy to come on and actually help tower for more than 10 mins at a time. Or who get bored with towering and just afk all the time while they are doing something else irl. If we had more than 3-4 actual active members we wouldn't still be recruiting this close to 1k. This is why we drop from 12 members to 6 in a span of 3 minutes then 3-4 that are left go afk and we lose the tower.
Idk if its just UFO or in most guilds,but it amazes me how you can have like 9 people on 5-6 will go afk and you will lose the tower. Then while your yelling at them to wake up to retake the tower then the blob or an event pops up they are all magically awake and ditching your towering efforts then when its over and you say lets get back to towering there all mysteriously afk again or in most cases just go offline.