The problem is that you are collapsing two users with very different needs into a single one.
1. If you are authoring an XHTML file, yes, you want the renderer to be as picky as possible and yell loud and clear if you make a mistake. This helps you produce a valid, well-formed document.
2. If you are an end user reading an XHTML file, it's not your file, it's not your fault if there are bugs, and there's jack shit you can do to fix it. You just want the browser to do its best to show you something reasonable so you can read the page and get on with your life.
XHTML optimizes for 1 at the expense of 2. HTML5 optimizes for 2 at the expense of 1.
1. If you are authoring an XHTML file, yes, you want the renderer to be as picky as possible and yell loud and clear if you make a mistake. This helps you produce a valid, well-formed document.
2. If you are an end user reading an XHTML file, it's not your file, it's not your fault if there are bugs, and there's jack shit you can do to fix it. You just want the browser to do its best to show you something reasonable so you can read the page and get on with your life.
XHTML optimizes for 1 at the expense of 2. HTML5 optimizes for 2 at the expense of 1.