Why change? Seriously. Monero is most interesting and you can already atomic swap between bitcoin and monero at will. Services like joinmarket already anonymise bitcoin without leaving the chain.

As for why not... Do you really want people blaming bitcoin when devs of their sidechain rug them while they are locked up for 3 months? Would they be right to blame bitcoin? Fuck no. Would the press have a field day and most normies believe it was bitcoins fault? absolutely.

TLDR, Drivechains is just shitcoiners trying to affinity scam. Why give them bitcoins shine? Why allow them to smear their feces on bitcoin?