I think a lot of this is technical debt. They built the feature/page/whatever code and it works "good enough". Now a future programmer three years later tells

I think a lot of this is technical debt. They built the feature/page/whatever code and it works "good enough". Now a future programmer three years later tells the business manager that they can do this much better now for $x. It will improve nothing as far as the user in concerned. Maybe the page will load faster but the user may not even notice. Maybe they will save some money on hosting and bandwidth costs. In most cases, the business person will most likely tell the programmer to keep working on to new feature z2021 project and leave the old code alone. This is until there is a security problem or the old code effects the z2021 project.