Oh, in fact there are many points

Paper bitcoins (or whatever) would allow physical exchange without anything going to the blockchain itself, ever. That would likely lead to higher awareness of common people about crypto and its advantages (you would be able to buy beer with it), thus promoting greater popularity of cryptocurrencies. From this perspective, it is a good thing

The problem arises when someone decides to create more paper bitcoins than there are real ones. But this issue can be dealt with if every paper bitcoin in existence means its digital version locked on the blockchain, the implication being that you can then spend only this paper bitcoins and can't create a transaction with their digital counterpart