Rental Agreement Utility

Why do we need Rental Agreement?? I have a question regarding the need of rental agreement from financial PoV. From my understandig, the tenant prefer agreement due to two reasons (i) HRA tax deduction claim in ITR which is not there in new tax regime. Need to have more than 8L in yearly rent just to breakeven with old tax regime (I don't have loans, political donation etc) (ii) To claim security deposit back in case things goes south with owner. But support from police and law is too limited in these cases, so not sure how much beneficial is rental agreement here. Most cases I know people have to give up. From owner PoV, he also needs to pay income tax on rental income. So I don't see much use for him also. But if the owner and tenant agrees without legal rental agreement, and can save taxes which can be used to reduce rent and increase effective earning for both parties. Owner anyways have upper hand in cities, and IT tenants not vacating the premises after notice period is very rare. So how exactly it is beneficial for any of the party? If anything, it is good for government only to take more taxes. There is no streamlines support for either larty from law and police. Want to discuss and understand PoV of fellow redditors.