Because, at least for the moment, it's unlikely that any company is going to offer that European $200k. It's about BATNA, not perceived fairness.

That said, this might change if remote work becomes a lot more common, and we might see a big flattening of salaries. Bad for SF real estate prices (and for high earners in those companies in general), since people in those HCOL markets will suddenly be competing a lot more directly with workers from elsewhere, modulo language skills, ease of scheduling, cultural fit, etc.