This may allow you to adapt views of extensions without completely overriding them. For example I may have requirement that all external links in my website should have
target="_blank" rel="nofollow noopener". I can create my custom helper with
a() method which will do that transparently, but if some extension uses static call to
Html::a() in its view, my helper will not be used. I need to override the whole view to change one
Html::a() to use my helper instead of basic one. With DI I could just inject my helper to extension view and extension will use implementation I prefer.