When cells are large, they cover more people. As a service becomes more popular more people will sign up. Since the single cell is shared by more people, the

When cells are large, they cover more people. As a service becomes more popular more people will sign up. Since the single cell is shared by more people, the speed will be shared around more, so there is a larger scale for it to degrade and the popularity will ensure this happens. Terrestrial cellular will have a fibre connected to it, and have a smaller area to cover and coverage is going to have less people, meaning the absolute top degradation will be less.