Japan also has a stagnant economy, so companies can't afford to get into bidding wars over talent and offer lavish salaries and benefits like they do in the US.
Or in other words, companies absolutely can bump pays, even with something not huge like 5-10% and they would still be fine, probably better even. But we can't have that when the CEO needs another yacht, or whatever it is that those empty people always chase. And it's somehow never enough.