Markup languages are designed to be computer-readable descriptions of documents. Programming languages are designed to be computer-readable descriptions of gene

Markup languages are designed to be computer-readable descriptions of documents. Programming languages are designed to be computer-readable descriptions of general instructions. Modern web applications (the sort of web site for which you would consider heavily using React, Angular, Web Components, etc.) are not really documents. It's really nice having a general purpose programming language to describe the instructions for such web applications.