they give you gains for holding your assets unless you have them in a wallet, it's like they charge you a fee for taking them out of your wallet and putting them into staking the gas

Some time ago I bought XRP and everything was fine, I put it in the earn option and I wasn't really convinced, my balance started decreasing and I researched and found that they charge you for the staking option, a kind of tax or something like that
Is this normal? Sorry for my ignorance, I am still new to this world $XRP