First of all, there's a huge technical challenge to what you're suggesting. Namely: how do you verify someone's identity? Considering how hard people take it when there's a mistake on their Wikipedia article, can you imagine what an uproar there'd be if a vandal was able to officially impersonate some famous person on Wikipedia?
It'd be a big deal, therefore the verification system would need to be pretty strong. That kind of system is very labor intensive and fairly bureaucratic, and not at all the kind of work you can get volunteers for, meaning it'd be expensive too. Basically, it's completely unfeasible for Wikipedia to do that - they can barely afford to keep running as is.
Secondly, you tout the "right of reply" like it's some enshrined rule of free speech that you get to write your comments on any web page that talks about you. Certainly people deserve the right to present their own subjective perspective on any matter, but there's a place for that - a separate web site.
Third-party websites play exactly the role you describe very easily, and a decent autobiographical site /will/ probably end up being referenced in a comprehensive Wikipedia article. Not as fact, of course, but as the claims of the site. This means there ends up being a citation link to a site where the subject of the article can write whatever they want, with no restrictions on verifiability or relevance. And those looking to Wikipedia for an encyclopedia rather than an autobiography can skip the link. Everybody's happy, right?