Negatives are capable of holding a much longer range of tones than any printing paper, be it b&w or color.

This means that because you see a detail in the negative, doesn't necessarily result in something that will actually be visible in the print.

Therefore, whether you print in the darkroom, or have someone else do it for you, and you end up with prints without highlight detail, it means the highlights in your negatives are too dense. To fix it you need to decrease development time to reduce contrast and highlight density.