Why a different wallet is created for both Okto and web3?

Updated 

The Okto wallet is a completely separate self-custody crypto wallet. The Web3 option on CoinDCX is an additional feature for CoinDCX users to trade directly on the blockchain and get access to the world of web3 (including trading on 50,000+ tokens and a lot more coming in the future). The CoinDCX Web3 mode is powered by the Okto Orchestration Chain, allowing you to get this experience in the most seamless way, right inside the CoinDCX App.