Question

If insectivorous plants can carry photosynthesis as they have chlorophyll, then why they trap insects and digest them?

Answer 1

The insectivorous plants grow in soil which do not contain sufficient nitrogen mineral. These plants (e.g. pitcher plant) are green and carry out photosynthesis to obtain a part of the food required by them. ... So, insectivorous or carnivorous plants feed on insects to obtain the nitrogen needed for their growth.

Answer 2

because insectivores plants do not have the sufficient amount of nitrogen for their growth as nitrogen is essential for their growth and this lacks in the soil where they grow.