Sadly in UK they are, even though in practice they can be challenged (since the right to work trumps it, basically). To be honest I don’t think they are much of a factor when it comes to compensation though. It’s largely a cultural issue: SV was largely built by engineers for engineers, so there is an awareness of what a happy engineer can deliver to a company. In Europe anybody technical is just that, a technical resource, a cog. That also links into the degree of freedom they are (not) granted, freedom to choose their tools etc.