This is a good take, and I've thought of it. The scenario that the stablecoin crashes, like LUNA, is one concern. The other concern is that... You don't know when bitcoin goes back up. We can all confidently say things like bear market, when we are already in a bear market, but what when we no longer are? Can you really predict when it goes back to $100k, and you sold it at $70k?
Many people have regretted selling bitcoin for fiat, with the hopes of getting back lower. I can't say the same for HODLers.
Well, converting your Bitcoin to any assets, even if it's a " stablecoin ", is already considered as selling.
I believe the easiest way to cash out your Bitcoin is to sell it to a stablecoin, and most exchanges have that. A few clicks, and you already have a stablecoin that is pegged to the US dollar. So for sure, that's why that is the most common way, especially for those panic sellers.