Yes, they are. It is proven by research that high NPS scores strongly correlate with companies' revenue and growth.
Net Promoter Score responses are declaratory in nature. Hence, measuring NPS is sometimes criticized. The criticism results from misunderstanding, though - the presumption that business leaders treat NPS as a sole predictor and guarantee of growth. It is neither of them.
Having said that, research proves the correlation between growth and high NPS scores.
A possible explanation is that readiness to recommend indicates customers' loyalty, which is a prerequisite for a company to achieve stable growth and profitability.
It's also proven that companies who have committed to implementing Net Promoter System - measuring Net Promoter Score regularly and across various organization levels enjoy increased revenue.
Sole tracking of the client's satisfaction levels gives companies tools to ensure the top customer experience. By having a Net Promoter System in place, they acquire a user-centric mindset that inevitably translates to higher customer satisfaction and loyalty.
In short, even if Net Promoter Score surveys are declaratory and don't guarantee recommendations, NPS makes a good metric whose tracking is important on a strategic level.