Frontend development is a tricky beast because its hard to separate business logic from view logic. Since all your code relates to the view, its temping to just stick all your code into the view component or controller. This makes your components huge, untestable, and brittle. An great frontend developer will keep extracting models and business logic from view code until the view code is lean and really only renders. Some things are easy to extract like http calls or parsing logic. Other things are harder to see - like logic that might drive a step wizard. Even code like this can be expressed in plain models with plain functions, but its a lot harder to see and extract. Most people don't get there, or just don't care, so many frontend codebases end up with spaghetti view modules that you edit and pray things still work.