Some people would prefer to keep their personal details private, or not share them with any or every person who uses AK. It is, IMO, not an affront to you or anyone personally, it is a personal and private choice by the individual member. That is their right under the options AK and its software choices makes. If you "want" to know more about a person whose details are private, I suggest you PM/conversation them with a request to follow, be followed, or share the information. However, don't be surprised if you receive no response, or a polite "no, thank you" or otherwise. That is not a fault, nor is it unfriendly, it is their preference and it should be respected, IMHO. As for AK, they give users lots of options for how you can share or limit information about yourself as well as how the forum software works for them, and most users appreciate that.
IMO, personal privacy in this internet age is quite under attack. When you view a page elsewhere, Forbes for example (certainly many others) or a site with Disqus or livefyre discussion options, they offer to sign you in with your Facebook, Yahoo, Google, etc. credentials if you don't already have an account with them. When doing so, their terms of use "allow" the site or the discussion software to "access" your contact list (everyone you know whose email addresses you have decided to use or collect). Why the hell would I want to share that with anyone, these are my friends, acquaintances, work colleagues, etc. whom I assume value their privacy as well. I don't want any site to access any more information that I deem necessary, and that includes the possibility of them sending "spam", advertising, offers, etc. to my contact list people. We already have enough of that coming from Spambots that harvest email addresses by scanning sites, or intercepting emails, or getting into email accounts and contact lists surreptitiously.
The only site I've allowed that info to be had is LinkedIn, primarily for the purpose of work and professional contacts.