I think the problem lies within the fact that many guild leves are just not worth doing. For people who would like to level a job to rank 50, doing guild leves with friends and linking the leves is the most efficient way to gain SP.

Now some leves only have like 4 mobs and those don't give nice SP. Other leves however spawn many mobs and give nice SP when 4 people link the same leve. It's not a question of exploiting, it's just being efficient.

If all leves actually spawned at least 15+ mobs and gave decent SP, there would be no need to cancel the good leves.

People cancel particular leves so that they have at least one good leve option after reset and that there are people able to link with yourself in parties.

I dread to think how slow getting to rank 50 would be if you had only those horrible leves that spawn like 4 monsters for 250sp each. o.o"