It's because LinkedIn is old in terms of web-age. Really old. They, along with thousands of other companies, had the need for a reactive web front-end when JavaScript had not yet matured to where it is now.
this plus lack of performance eval/culture/strategy to grow responsibly and enable future success
its a great learning experience though despite what people say about the inability to learn the new hot hot tech. the nuance of software development is the decisions that other people make, that is inescapable and is a skill worth developing. i'm not buying the "just do a startup" because i think its a cop out.
