To further elaborate on this, the main point of margin trading for me is that you can get additional bitcoin exposure even if you're balls deep, all-in, with no significant fiat left. If it goes belly up you lose your preciouz, but if it goes well you get paid in btc straight away. In udder words, as someone sez, you get to stack additional sats just because the corn got higher. It's the opposite of cashing out - more akin to cashing in.

Note that it isn't necessary to leverage above 1:1 at all. Even 1:20 leverage will do - say, a 0.05 btc order when you have 1 btc in the trading account. In fact, it's preferable to keep the leverage as low as possible because that limits liquidation risk.