Purchase of property ( resale flat)

Why in Mumbai only Agreement for sale is entered into while buying a property ( ready to occupy flat) and that itself contains all terms and conditions of sale as well as condition for title transfer once the full payment is made by buyer to seller! Since partial loan is taken from the Bank to finance the balance purchase consideration! Bank does not fund unless stamped and registered Agreement for sale showing own contribution receipt and balance to be funded by Bank on or before a particular date is mentioned in the Agreement! Hence this Agreement for sale containing details of property, terms and conditions etc is stamped and registered which is accepted by Bank as title deed for the property! There is no second document prepared like sale deed! So my question is does this stamped and registered Agreement for sale will not become title deed or ownership title deed for the property acquired? Never heard people going for separate Sale deed registration etc! Can you clarify the same !