The combination of reputation score requirements for site interaction and the heavy splitting of the website into many similar but slightly different sub-sites with independent user accounts creates a frustrating situation for non-power-users.
Here are examples from some situations that I frequently find myself in:
A search for answers to programming-related topics leads me to a page on a Stack Exchange website with a posted answer that seems promising
The posted answer does not work for me, or I could use clarification on the answer; posting a comment on the answer would help solve the issue
It turns out that I am not allowed to post a comment because the question is posted in an obscure Stack Exchange site for which I have no reputation points, and my only option is to post a new question when all I really need is clarification on the previous answer.
Case in point: Boxplot for several distributions?
I find answers to relevant questions on an obscure Stack Exchange site which I have never used before, and I decide that it would be an appropriate place to post my own question on a similar topic
After doing a lot of research on the question, I try to put together a quality post with plenty of cross-references to help keep the site's content cross-linked and to help with Google searches
Due to my lack of reputation on said site, my ability to include links in my question is restricted, leading things such as this embarrassingly butchered post: https://webapps.stackexchange.com/questions/95430/private-development-to-do-list-for-an-organizations-public-repository
Does this really constitute the site designer's intentions for the site, or is this an unfortunate side-effect of what Stack Exchange has grown into? Take my own account, for example: http://stackexchange.com/users/6989882/user5359531?tab=accounts
I am currently a member of 17 different Stack Exchange sites. 9 of these are directly related to programming in some way (possibly more, subjectively), all with very similar content. Yet I can only post without restrictions in 2 of these sites. I have maintained this account for almost a year now (SO) and use the website daily; the fact that I still cannot post without restrictions on topics I am familiar with or seeking help on seems quite ridiculous.
The obvious solution is to simply post more answers and get more reputation points, but this begets the title question: "Why is Stack Exchange biased against casual and cosmopolitan users?" If I do build up rep posting answers to R questions in Stack Overflow, I find myself unable to even post a comment on an R question in Cross Validated. Posting worthwhile answers and questions is no small task either, considering that the sheer size and amount of covered by Stack Exchange sites means that in most cases, your question/answer has already been posted.
Is this a topic that the site designers care about enough to devise a solution? Or have we just accepted that "this is the way it is on Stack Exchange"?