Maybe someone will make a Bitcoin mortgage at the pawnshop and if the pawnshop agrees, this person probably does not have enough deep knowledge about Bitcoin, this is the only reason I can see.
People pawn their items because items are not currency, it's not easy to move it around, it's not easy to sell them, you can't really sell your items that easily, it would be quite tough. So, what could you do? You would be able to actually make a big deal out of it by just pawning your items and getting them back with hopes that it won't be sold until you get back, but currency could be used everywhere anyway and bitcoin is a currency.
that is true, there's no need to pawn your btc. just sell it and buy when you have the funds. why make your life so complicated with these things. this is why i don't like many crypto lending apps, they will ask for collateral and then you still need to pay for the interest. so why not sell directly your crypto? think of the trouble that you're going into if you will use these lending apps. at least, you don't owe anyone as you are using your own funds.
If the price of the bitcoin will goes in an uptrend market and you make a collateral with your bitcoin lose at your end that selling partial of the bitcoin so the profit cames from the price movement can be use as payment.