"Being an alien from Alpha Centauri, and observing the growing collection of programming languages, what do you think people keep designing new ones for? Why do some Urplatians argue for Scheme and other Urplatians for Python?"
Most people model other people as just like themselves, plus or minus a diff. The trouble is that they don't understand just how wide-ranging human thoughts and feelings can be, and assume they will understand and be able to model based on the diff, even if the diff is larger than their whole mind.
It's why geeks keep coming up with "intuitively obvious" schemes no-one else can understand, and why engineers are routinely surprised at what actual end users do with their products in user testing.
So people write new languages that suit their personal peculiar ways of thinking. Thankfully, many are quite aware that this is what they are doing and don't claim universality.
This is why Urbit is art: translating numbers and ASCII characters into nonsense syllables that you are actually expected to pronounce and think in suits Yarvin's mind, even as it leaves me thinking "there is such a thing as being too much of a Borges fan". Which is absolutely fine. But this is why Urbit is art (an expression of a unique personal vision), not anything people are actually going to use without similar levels of confusion to the present.
For an example of fully rampant Typical Mind Fallacy in Urbit, see the security document: http://www.urbit.org/2013/08/22/Chapter-6-security.html About two-thirds of the way down, you can actually see Yarvin transform into Moldbug and start pontificating on how humans communicating on a network should work, and never mind the observable evidence of how they actually have behaved whenever each of the conditions he describes have obtained. The very first thing people will do with the Urbit system is try to mess with its assumptions, in ways that its creators literally could not foresee (due to Typical Mind Fallacy), though they might have been reasonably expected to (given the real world as data).