For the normal user it does not matter. It just matters that there are competing engines. As long as there are multiple implementations, we will have a formal

For the normal user it does not matter. It just matters that there are competing engines. As long as there are multiple implementations, we will have a formal standard for HTML and Co. If e.g. everybody (Microsoft,Mozilla) would adopt WebKit, then nobody would bother to extend the HTML standard. Just implement it in WebKit. Soon, HTML will be a mess like Office Open XML.