I've long since stopped asking why, and just gotten on with "why not?"
Building a replica of a platform gives you the experience of doing it, the understanding of the process, familiarity with the tools you're using ... and possibly some bragging rights among your fellow nerds.
Why pimp out your CPU case with neon? Why put spinners on your rims? Hell, why have cars anything other than black, which should suffice for anybody? Why play video games? Why watch TV?
None of these accomplishes anything other than filling in time or soothing your own need for something you think is cool.
To you, it's opportunity cost. To someone else, it's "why the hell not?" It's something to do they find amusing.
Compared to half the crap you see on YouTube or anywhere else with humans ... I don't see this as being worse than anything else.
With all the dumb crap humans do every day, there's at least some coolness to this.
And I'm betting you can identify at least 10 things you do every week which you couldn't answer "why" if pressed on the issue.