I think the reason why they have these options is to help the community or traders to get fewer fees
That's quite naive.
Their own centralized coin is now worth $100 billion. If they wanted the community to have lower fees, they could simply reduce withdrawal fees.
They've created their own coin to make themselves rich, which is exactly the same reason for which thousands of other coins have been created.
I'm using some of them TRC20 and BEP2 just to reduce the withdrawal fee when transferring them to another wallet
If you transfer Bitcoin to a wallet, you know for sure it will still be there 50 years from now. If you transfer some made-up token on a private centralized chain, it could be worthless tomorrow. Keeping those private tokens is just as dangerous as keeping your coins on an exchange: "not your keys, not your coins"!
Now imagine a few more parties want a piece of the pie. What's next: dozens of different withdrawals options to confuse users away from using the real Bitcoin?