All IOST users are deemed to have agreed to the Service and authorized KuCoin to make use of their respective IOST assets on behalf of them for Internet of Services mainnet staking.
So if you don't want to participate in the staking of kucoin, get your IOST out of the platform.
See more details here: https://www.kucoin.com/news/en-iost-soft-staking-official-rules-cash-back-investment-program-for-internet-of-services-iost-holding