Please consider that as a (presumably young or young-ish) European, you have access to different educational resources, and are exposed to a cultural context where English is the lingua franca. As a Bulgarian, or any other European nationality, the only foreign language you truly need to learn to get by almost anywhere on the continent is English.
There are many, many countries and places on Earth where English is a significant barrier, due to being much further away, geographically and culturally.
While English is unavoidable after a certain level (just like French is unavoidable for a chef, or Italian is for a musician), it is crucially important that the barrier to entry does not also necessarily come with huge a language barrier up front.
I am Bulgarian, living in Bulgaria, a small country in Eastern Europe. My native language is Bulgarian. I also know English, Russian, and a little bit of French and Turkish.
I do not want to write, or read source code written in Bulgarian, or Russian or French, or Kiswahili, or Japanese etc. I want to use one single language for that. It currently happens to be English for historical reasons.
Supporting unicode in source code, will lead to language fragmentation, and will limit my ability to participate, and to understand everything already build by others.