Lacking a very rarefied community capable of self-moderation, like this site has or some specialized reddits and forums, the no-real-name becomes a major drawback. A minority of douche-bags will generate a majority of noise and will come to shape that world in their image.
This is quite visible when browsing Mastodon instances, many of which look like a crossbreed of 4chan with Myspace. Most accounts don't have a real picture. The fact people assumed their real identities, cared about what they said and did, and that you could find real people knowing only their name was one of the key ingredients to the success of early Facebook.
Furthermore, the whole "no data collected" has any value from the perspective of the user only when using real names. Otherwise, I really couldn't care less about data attached to an anonymous account.