All airlines now dispatch with minimum legal fuel plus what delays are expected. The captain decides if it adequate and adds what he feels is necessary. I rarely added fuel if it was reasonable but once out of Honduras to MIA realized we would probably hold so put on extra fuel.
We hit a turkey buzzard right after take off right above my window so hard I thought we had popped rivets so instead of FL410 went to FL280 in case we depressurized. I couldn't have done it without the extra fuel to land at MIA. The PIC does not ever have to accept dispatch fuel if he disagrees with it.