If you know a lot about something, and other people know that you know a lot about that subject. For those interested in that subject, it will be natural and logical consulting your and your views on the subject. And vice versa, if you don’t know anything about the subject, your views aren’t really helpful for anyone or anything.
A brand ambassador or an influencer is “handy,” when you need a specific segment within your public. This would most likely be a segment who are attracted or responds better to other or different attributes than you or your company have cultivated so far. Hence they are amongst your target audience, but so far your efforts to gain them as clients or customers have been unsuccessful.
A proper influencer or brand ambassador strategy can be extremely successful and cost-efficient. However if traits, competence, and segment aren’t properly aligned, it will be a complete and costly waste of time.