> Many "engineers" using React or AngularJS actually don't know how the DOM really work, like many people only know jQuery and not standard DOM API in order to

> Many "engineers" using React or AngularJS actually don't know how the DOM really work, like many people only know jQuery and not standard DOM API in order to perform a task, or many "engineers" don't know how to write CSS so they use Bootstrap. Many know how all these things work but prioritise your first reason "code you don't have to maintain and test".