In recent years new protocols for externalising data have become popular. Schemes like Protocol Buffers & Avro are in common use.

Stellar uses XDR, a scheme from the 1980s which is (as far as I can tell) not popular in recent years.

I don't question the decision, but I do think there might be some interesting and compelling reasons for choosing XDR over other formats.

Why was XDR chosen?