- influencing investor or consumer confidence. Even if you don't have high confidence in what you're saying in the long term, it may be necessary in the near term to make statements that project confidence
- building a brand as a thought-leader, futurist, whatever. In part this depends on saying something interesting that people will want to read or hear about. People can enjoy this kind of prediction without believing it. A book review for Kurzweil's The Singularity is Near said "exhilarating speculation is great fun to read, but needs to be taken with a huge dose of salt." Buckminster Fuller was wrong about many things but people still enjoy his work because it's interesting.
https://en.wikipedia.org/wiki/The_Singularity_Is_Near#Review...
- influencing policy in your preferred direction. No one can predict the number of severe zoonotic diseases that will have epidemics in the next 30 years, but some experts think they'll happen more frequently as the climate crisis progresses. We might all be better off if experts understate the uncertainty in their projections when they make their case to policy-makers.