Businesses of all kinds offshore labour: small, medium, large, public, private, sole trader, partnerships, VC funded[0], bootstrapped, profitable, loss making, you name it. They all do it for what, for them, are rational reasons. Often very boring reasons. Offshoring can be the difference between profit and loss, the difference between a business that is sustainable and one that is not. A failed business can't employ anyone, whether onshore or offshore.
Now you can argue about whether a business that isn't sustainable without offshoring should exist at all, but that is straying further off topic than I care to go, and frankly is also another rabbit hole likely to lead to unhelpful oversimplification.
You might like to imagine gleeful scheming and maniacal laughter in the boardroom, but I'd confidently bet that that's almost never what's going on in the vast majority of businesses.
[0] You talk about "publicly raising millions": raising funding is not what the vast majority of businesses spend much time doing, and it's not what most businesses who use offshoring spend much time doing.
This is different from hiring a remote employee to your company where you've advertised a salary range as part of the job description.
In my experience that's almost always how it works because you have to employ people in such a way that you abide by all local laws. I have seen people employed as independent contractors but, and again this varies by country, there are often restrictions around criteria like how long you can do that for. It's also kind of a PITA for the "employee" because it means they might have to do things like sort out their own taxes and healthcare. If you have a legal entity in place you can do that for them. That means you either set up a subsidiary, or you using a local offshoring firm. And this applies regardless of the country.
Fo you want to wait for the whole world to change or just have that senior dev make better decisions for himself
People that run business know that they need to keep a coherent symmetry on some level in how the team is structured and how they're compensated.
Save money by paying some people on your team less based on where they live.. yea, for those that think it's a good idea, good luck with that..
How much perverse pleasure do you think is a reasonable amount when they save a few thousand dollars a month, while at the same time publicly raising millions and paying developers junior than him more money... and doing everything in their power to burn more money to get ahead of the competition...