Holding BTC for the long term has historically been a lucrative investment. Just not holding it on one of the many centralized exchanges that always seem to get hacked or go bust.
It's not a "lucrative investment". It's a bigger fool scam. The only way to make money in BTC is for someone else to buy in for more than you did originally. It makes it appear as if BTC's price is always going up, but in reality the number of fools is limited - especially with the buy-in getting higher and higher.
Sure, the price will always go up in the long run. But it will become less and less liquid, and at some point those who are left will have hundreds of thousands or millions of theoretical money that's completely unspendable, because no-one else will buy in for more than they did.
> The only way to make money in BTC is for someone else to buy in for more than you did originally. It makes it appear as if BTC's price is always going up
I'm not a crypto expert but that statement seems incorrect to me, since as far as I know BTC has deflation built into it. The more is mined the harder it is to mine more. So as long as investors are keeping some trust in it and are not selling at large scale, the BTC value should continue to go up in the long run (ignoring smaller fluctuations). That's why people have been flocking to it in the first place.
The person you're replying to was very careful to say "has historically been a lucrative investment". They have not claimed it to be a lucrative investment right now.
I can list a number of valid, real-world use cases. Bitcoin can be easily held either online or offline, in a number of solutions ranging between paper wallets, through hardware wallets, to dedicated laptops.
Holding bitcoin on exchange is like giving people the keys to your safe because it is easier if they can open the safe for you while you gamble.