Exactly. What happens when all tech stocks and real world companies are replaced by nothing but Goldman Sachs, financial vehicle, proof of stake coins? The world collapses. This is obviously not a sustainable model. When government gets involved making Bitcoin laws, they're either going to come down on proof of stake coins hard, or they will have the same relationship how Wall Street currently exists, to enrich insiders and screw over everyone else.
"Interest" is not really something I want to see survive in the Bitcoin protocol's future. The idea of trying to replicate the current, broken financial system is outrageous.
I don't see any particular reason that a government would decide to regulate PoS/PoW hybrids different than PoW coins or PoS coins. In the end it is the same concept: the blockchain needs to be confirmed by multiple peers to ensure that transactions cannot be duplicated, faked, etc. so in exchange for adding and confirming transactions to the blockchain the miner receives a reward in the given coin. It really doesn't make a huge conceptual difference if the transaction was confirmed via PoS or PoW, the point is that the miner receives a reward for using their resources to keep the coin running and confirming the blockchain.