You can do that with permissively licensed software too. Except with those, the party distributing their repackaged version doesn't have to distribute source code alongside it. A lot of companies avoid copyleft software because they don't want to or cannot deal with stricter licensing terms. If you're a company creating commercial software which you intend to sell, you don't want to use any GPL code, because you want to keep your software closed source to avoid exactly what you described from happening.

This can be exploited by primarily licensing your open source code using strong copyleft (like the AGPLv3) while selling commercial licenses to businesses that don't want to comply with the AGPL and are willing to pay up. Qt is able to successfully use this even with weaker copyleft (LGPLv3) because it's used a lot in embedded systems (like smart cars) which cannot comply with the LGPLv3's anti-tivoization clause.

This means copyleft licenses can make it easier to profit if you're the author of the code, but of course third parties can more easily profit from permissive licenses.

Torrenting has existed for a long time, yet people still buy software. There is a lot more to software distribution than traditional product sale.

You want to have frequent fixes, compatibility with modern tools, new features and a trustworthy distribution pipeline. These are all things people and corps are willing to pay for in FOSS software.