When some amphibians mature they live on land because

They develop adaptive features like lungs, legs, skin etc.

Explanation:

Amphibians are one of the classes of animals. They are group of animals capable of living both in water and on land. During their early stage of growth as tadpoles, amphibians live in water using their gills to breathe. However, as they grow, they develop certain features like legs and lungs that enables them transit to living on land.

Amphibians start off their life in water and slowly get adapted to living on land as they mature. Most mature amphibians breathe through their lungs and skin, which they developed as time went by.

this is a good question! i'll do some research and come back when i have the answer!