Why do fleshy fruits often have seeds with very tough seed coats?

Answer: The seed can survive in the gut of the animal.

Explanation:

The fleshy fruits are consumed by the animals. It is protected by the seed coat because the seed can survive in the gut of the animals.

The seed is safe in the gut of animals so that the seed is not destroyed and is used for the process of pollination.

The seed if will not have seed coat will be destroyed inside the gut of the animal and will not be available to for the process of pollination.

The fleshy fruits are the fruit which contains soft and fleshy ripened ovary which is usually sweet in taste like the berries and the mangoes.

The fleshy fruits become fleshy as an adaptive mechanism of seed dispersal. The fleshy part encloses the seed with a hard coat as an adaptive mechanism.

When the fleshy part is eaten by the animals, the smaller seeds can be passed down the digestive tract of the animals unharmed and undigested.

The toughness also protects the seeds from the mechanical pressure is applied to the seeds.