Not necessarily because it'll be worth something 
down the road, but because owning a piece of a 
production they particularly enjoy is fulfilling 
in it's own right. No two identical productions 
cels exist, in theory, so having a unique shot 
of a favorite scene is worth it to many, 
regardless of condition.

Besides, stuck sketches are just about the least 
of cel collector's worries... 

Again, IMO...