Portuguese guy here, but isn’t this just a direct consequence of the perfectly divided electoral system? If your voters are all X-language speaking, they (the voters) don’t really care about your Y-language level. I was surprised to learn that even in Brussels the electorates are divided by language.

In other multilingual countries being a poliglot is a great political advantage, I’ve just read about this unlikely white gay mayor in a mostly black town in South Africa. His secret? A rare white Zulu-speaker.

In Switzerland if you’re running in a bilingual Canton you’re also expected to speak both and if you aim for national politics you know German is essential.

But here you can always build a career encapsulated in your own language bubble. People normally learn languages because they need or feel it will bring them a big advantage. If it’s just a “nice thing to do” most won’t.