Drivechains are awesome because they allow for financial experiments that benefit bitcoin. There are two chains that do stuff that a small number of real people seem genuinely interested in: eth and xmr. But to use these chains, people have to buy altcoins, which harms bitcoin slightly and benefits scammers immensely. Drivechains make it so that the features of eth and xmr exist on chains where transactions sill benefit bitcoin. The users of an eth-like drivechain or an xmr-like drivechain would not have to buy an altcoin to use them, and all fees paid to create drivechain blocks end up in the pockets of the bitcoin miners who help secure our coins. So yeah I'm a fan.