People have been building replicas of this stuff for centuries. It can bring the community together, and hey, the specs are in Bible, so why not?
The Tabernacle is God's pad, where he'll "dwell among" the Israelites (25:8). Apparently he's pretty picky when it comes to living situations, so he gives his people some pretty detailed specs on how to get the thing up and ready. This is going to be one nice tent:
Just like with the Ark, these are urban instructions: you don't think about building nice tents during a stroll in the desert—you think about surviving. Only once you're out of the desert do you have the luxury of thinking about fine twined linen.
But if you're going to connect your image of God to something physical, then that something has to be magnificent. Ever wondered why the Vatican is a huge complex filled with art and gold? Same idea here.
Cubits are the main unit of measurement for all this ancient stuff. Traditionally, it's measured as about the length of your forearm—20 inches or so (source). They didn't exactly have a meter stick handy, so why not use what you've got?