It is sometimes difficult to get commitment to implementing an idea. Maybe there’s some doubt from certain stakeholders, even after you’ve presented evidence for an idea. Maybe there’s reluctance to invest budget & time in the idea, particularly if it’s going to require a decent chunk of both.
Sometimes, user testing on 6 participants doesn’t provide enough confidence that an idea will work.
However… sometimes, we can implement ideas without actually fully implementing them – just to get a feel for demand for it.