Bonjour Kushagr,

A similar point was raised some time ago.

Here is the link, and the others from it -- I think that you will find it all very interesting.:-

https://kwiziq.learnfrenchwithalexa.com/questions/view/j-ai-vs-je-suis

Bonne continuation,

Jim

Just to repeat what's been said in the linked posts already: la soif and la faim are nouns. Therefore you are having them instead of being them. In English, "thirsty" and "hungry" are adjectives. Therefore you're being them and you're not having them.