Even if they don't sell the code to the customers directly (or even binaries, because that's what most customers actually care about), somebody in the chain is selling that software to the end customer and that money is going up the chain. It's kind of obvious really - if the work you're doing isn't creating saleable value, then your company won't be able to pay you.

But there is far, far more in the world that just SaaS or internal only software. Sure, companies are generally shifting towards SaaS (in part because it allows them another way to combat piracy, but also to extract recurring revenue rather than one off purchases), but there's still plenty of software you can go out to the shop and buy. Most of that wouldn't exist without copyright laws, because those developers would have found some other way of making a living instead.