So you know how it is when you need to make things: you have raw materials. You don't have only enough for the next project - why constrain yourself? - so you accumulate more raw materials so that when an idea hits, you can find the right stuff for your project.
What this means is that you keep getting more stuff, often faster than you can use it up. So you figure out a system to store it, and then you reorganize your stuff into your storage system, acquire more stuff (still faster than you use it up), rethink your storage solution and do some more organizing.
Part of the organization process is prioritizing and figuring out what can go into hard-to-reach places (stuff you use only rarely) and what should be right where you need it. This means that things get taken out of one space, then they get shuffled around, then things get put into the empty spaces.
Sometimes people climb into the temporarily empty spaces.
They fit quite well, don't they?