This is a question that is often asked of model rocketeers by persons who are casual observers of the hobby and haven't ever been bitten by the rocket bug.
"Wouldn't just one rocket suffice?"
" Do you need so many?"
Answers:
"No!"
"Yes!"
This whole thing can be summed up with a simple math equation:
If X equals the number of models a rocketeer wishes to have, or has to have to complete his/her collection,
and N equals the number of rockets currently in that collection, then
X=N+1
Cheers!