[elephantum]

That's what Lego does.

It seems almost intentional that each set has several rare pieces that can not be found in other sets.

[jacquesm]

You can forget about the 'amost', it is intentional and has been for many years. The time that you could build a model perfectly from the bricks you already had is long gone.

[guepe]

I think that's what make a model such a nice experience. It's different than building yourself: you end-up with something that looks definitely better than an amateur build. You didn't work on imagination, but end-up with an amazing build. Then you can use those unique pieces to put some highlight into your own build !