If you think about code quality in terms like line length, spelling errors, etc it might not matter.

If you think of it in terms of:

- how long does it take to get at new developer up to speed? (everything from readability to build systems)

- can this be hacked any day of the week if someone puts their mind to it? (both own code and libraries)

- can we be resonably sure that new changes don't introduce (large) defects? (testing, modularization)

it becomes impossible to argue that it cannot affect business success.

Yes:

- it might work as long as the old dev is happy and alive, but break down when he isn't available anymore

- it might work as long as nobody targets this business specifically

- it might work as it exist now but at some point be impossible to update anymore and the day new tax rules or whatever are introduced, it breaks

Everyone makes these claims, but I've worked at multiple successful companies with atrocious onboarding and code quality. A few people always make the claim that the software will become impossible to update or the system will collapse, and it never happens, even after a decade or more.

At one place I worked we were we were in a monopoly position and multiple companies were forced to buy from us.

Still we were barely were scraping by.

We were forced to spend a lot of time to do tricks to make Windows 7 behave like Windows.

We couldn't take opportunities that showed up as the only ones who knew the software were SW engineers in another country, and they were unreliable.

We could have lived comfortably since our software was almost mandatory and we were the only supplier.

But we struggled badly and pay were late on multiple occasions and I was happy to leave after some years.

Well this is just wrong, so I don't really know how to respond. You're probably thinking about monopolies such as Facebook, Google, or the like, where not only does code quality not matter, but not much matters at all. Most businesses do not have this luxury.

Nope. I'm thinking about every single company I've ever worked at. My previous job was in healthcare and most of the software in the entire industry is atrocious.

I guess if my rep sheet was McDonalds, Subway, and Tacobell I wouldnt think food quality mattered either.