[fryguy]

The main purpose of adding sidechain support to bitcoin is to allow coins to be "burned" on sidechains in order to get them back on the bitcoin blockchain. It's already possible to have unidirectional burning from bitcoin to other chains, but not bi-directional. There are lots of things to get right though which is why it's taking a long time to do.

It's not necessarily the case that it's permanently pegged to an exact bitcoin amount. Perhaps they way that miners of the sidechain are rewarded is by inflation/devaluing how much bitcoin the sidecoin can be burned for. The point is though, it's not market effects that are causing it.