People would absolutely be more engaged and more excited about their work if they were paid more. The only reason people work is literally for money…
Well, yes, but also that's super reductive.
The primary reason people work is literally for money. The specific _place_ people work is for things that interest them, engage them, challenge them, provide a path for continued growth in their career, or contribute to a common good they believe in.
And I would argue that it's not necessarily a given that people will be "more engaged and more excited about their work if they were paid more," but instead, may be willing to stick around in an unengaging, unexciting environment _longer_ when they're paid more.
Theories like Hertzberg exist for a reason and show that money isn't even close to the most important thing for people to work for. If the money is good enough, there are many other factors that are way more important. Not enough money is a reason for people to leave, getting more money is hardly ever a reason to work harder. The possibility of getting more money if they work harder is a good motivator though, once they have it that stops.
In most software engineering jobs, people have enough money to live an enjoyable life. At that point, having more money is not really such a strong motivator.