I'll start by saying: I'm massively risk-averse and I also don't believe in holding debt.

That said: getting rid of debt is going long on fiat, not short. If I borrow $1m from the bank and use that money somehow (e.g., to buy BTC or a house), my net position is -$1m. I'm happy to hold that position if I assume that the value of that $1m will go down over time.

If I took out that loan in BTC terms instead, I'd be shorting BTC, and we can all appreciate the insanity of borrowing 4 BTC to buy a home today and having to pay that back in 10 years, when the 4 BTC will almost certainly be worth far more than the house.

One final mental model: "selling short" is essentially the practice of borrowing an asset and then selling it immediately, which is exactly what most people do when they borrow fiat.