Why do you have to "Wrap" ETH before you can use it on DeFi ??

Why do you even have to "Wrap" ETH in the first place in order to put it onto a staking platform??

I'm looking into the new Spool V2 platform.

You can put ETH on to their staking platform, how ever you have got to first turn your ETH into wETH first using Uniswap DEX. Which obviously cost a gas fee.

I thought that the whole point of ETH was that it was to be used as the reserve currency for the DeFI industry?

Thanks.