Why specify type?

Question

HTML

In HTML5 I write tags with <script>or <link>without the type attribute and everything works fine. But when you look at the code of other sites, these attributes are everywhere.
Question: Why is this attribute needed and what will happen if it is not written?

Answer 1

For HTML4.01, this is a required attribute. Not for HTML5. And type can contain not only text / javascript, but also text / vbscript, for example

Answer 2

That's right, the type attribute for script and link tags is now (in HTML5) deprecated.
All sites must migrate to HTML5.