Probably because Levels says he codes each product in a single PHP file. But then again, there's a reason he's successful and the parent is not (at least to that same level, pun intended). Technologists think code is an end unto itself while true entrepreneurs that it's just a means to an end, and that the end itself is money (otherwise, why are you running a business? If you don't make money, it's simply a hobby).

>it's just a means to an end, and that the end itself is money

The end is also to create something useful for your customers. Hopefully.

single file 30,000 of PHP code.

That truly doesn't matter though. It's certainly not what I would do, but assuming the numbers he claims are genuine, it's hard evidence that your customers don't care how you wrote the software.

The feature of software being maintainable and reusable by people other than its original author is for the users. It can be easy to forget until it’s too late.

The users don't care about this.

I write my software with Haskell, NixOS, comprehensive testing, static analysis, linting, a great deal of care, etc.

If I had written everything in one big PHP file however, the difference to a paying customer would be exactly nil.

1 file can be very maintainable. Reuse is promoted by a well designed library and interfaces, which can also be in 1 file.

Only thing 1 file can't do is allow concurrent work if bad version control is used. If patches are tight with good patch theory, 1 file is fine again.

Modern programming languages have namespaces, catch type bugs, all of it works quite well with 1 file. Recent OAuth Cloudflare 1 file library (coded a bit with AI) is a breath of fresh air, 2600 lines of data types and behavior in one place.

like his flying simulator.