Why do LEGO pieces come in small plastic bags in each box?

LEGO puts its pieces in small baggies to make the job of packing a box cheaper and less error-prone. When LEGO wants to include elements in a set, they have to gather together all the elements necessary, and put them into something. read more

LEGO needs to pack 237 pieces of 78 different types into the set. If they put it all in one bag or box at the same time, they'd need 78 different elements on the packing line, all at the same time. That's a lot of them. They'd also need to QA a bunch of boxes off the line initially to make sure they were correct. And that's a lot of things to check. read more

The primary one is building order. For the last 10 years or so, LEGO has used numbered bags, in the order that they're used in the set's creation. So for some sets that come with specific build instructions, they'll put pieces in the bags according to which ones are used first. After that, the biggest factor (I believe) is weight. read more

If you lay the bags flat and spread out the pieces, they do fill the bags. When put in bags that can be flatter (but use more plastic), it means thinner boxes can be used, which reduces paper used. TLG actively tries to reduce box size and other resource uses to move towards more green practices. read more