It's not really, but the difference is that I'm limited by the supply of BTC, and it requires that I actually have the money to make the 'bet' at the start. That restricts the size of the spot market.

If I'm buying futures I can enter into a contract that says "I'll buy a contract for 1BTC that says BTC is going to go from $88.5k to $98.5k in 1 year." I don't actually hand over any money. In a year's time, if BTC is now $100k the person who agreed on the contract gives me $10k. If it doesn't go up then I owe the seller $10k. The futures contract is settled in cash - no BTC is involved.

Right now though, I don't have a $88.5k to spend on BTC, so the spot market isn't an option. I probably could find $10k in a year's time so a bet on a BTC future might be viable. The actual derivative 'value' isn't real though. The only money changing hands is the delta of the change in value when the contract is settled.

(Caveat: I am a total noob at finance stuff so this could be quite wrong. One of the many reasons I will not be buying that futures contract. :) )

Derivatives can be structured in a time-constrained manner that requires them to go up/down in a specific time window, thus amplifying the gains/losses. Also there's generally no way to short an asset without borrowing them with a contract to pay them back (which requires timing the market move and paying rent on the asset). This is something that options contracts solved.

Its hard for me to consider owning the underlying asset as gambling compared to owning paper bets on the future value. In the former you are owning it today, in the later you are betting only on what it will cost to own later.

You might buy BTC to actually spend it, say on paying a ransomware vendor.