What’s the drawback to 3x daily leverage funds if I’m heavily bullish on something?

If I’m bullish on something long term and the annual fee is only 0.75% and I can also purchase such shares in my tax free ISA account which makes it much cheaper than margin. What are the potential drawbacks? Of course it could drop 30% and I’d lose 90% but I would invest even more aggressively in that case and be ok with a longer time frame.

I know people say they aren’t ideal but in the UK it’s the only way I can utilise leverage while being completely tax free.