its a test bed as Justus put it to stop Bitcoin type innovation making it to the Bitcoin. if a SC innovation gets traction you bet it wont be adopted, the incentives are the wrong way around.
Whose incentives?
If we use the same ledger who gets any more incentive for using one particular chain or the other?
Nobody has answered yet what the revenue model for Blockstream is.
Until they explain themselves, it's reasonable to assume they intent to derive some financial benefit from the existence and usage of sidechains.
In that case, clearly any innovations in the main chain that reduce the need for sidechains are a threat to the revenue of Blockstream.
Unless they offer an alternate explanation of how (or if?) they intend to repay their investors, this looks like a severe conflict of interests.