You can't really compare US and Norwegian unions apples to apples. They don't work the same way. In Norway they're way more mainstream, work closer with the government, and they don't employ people. There are no "union shops", and no vote to join a union. You just join one while employed directly with your employer.

You can still negotiate your own compensation, but the union may also negotiate raises for the entire workplace separately (including for non-members). In a way you could say the union negotiates a workplace-specific minimum wage.

The risk of union workers getting fired and replaced with scabs is far less in Norway, because there is much stronger worker protection. These protections apply to everyone, not just the unionized workers, but they were achieved due to unions, years ago.

I don't think you necessarily can draw any conclusions about strategy for Norwegian unions based on experience with US unions, or vice versa. They're just different beasts.

Note: Apologies if some of this is mildly incorrect, I have not been directly involved with union work in either country, and so I only have a high-level view of it all. Someone more experienced should be able to give more detailed information about union strategy in either country.

IMHO this strategy helps to prevent chewing. Workers will say "I need this union for a high wage" instead of "what do we even need these union dues for anymore".