Can they all be amalgamated into the main site with their own tags?
The reasons I can think of that this is a good idea are:
There are a lot of questions on the child meta sites that are duplicates of questions on the main site.
The child sites do not offer any reputation points and so the questions/answers cannot be taken seriously.
The main site would gain more traffic.
A lot of the child sites for the smaller sites are never used.
No.
Yes, given sufficient time and funding the developers could adjust all those formulas and make exception for posts tagged [meta]. But I'd rather have them spend valuable time elsewhere.
- There are a lot of questions on the child meta sites that are duplicates of questions on the main site.
No; there may be questions which have duplicates on Meta Stack Exchange, but not on their respective main site. There's a better way to fix that than dropping child metas altogether: Could we allow child Meta questions to be closed as duplicates of Meta.SE ones?
- The child sites do not offer any reputation points and so the questions/answers cannot be taken seriously.
You're entitled to your own opinion, but I disagree. For users into it, the badge system still provides enough gamification; me, I'm just happy to share my knowledge about Stack Exchange across the network, not just here.
The main site would gain more traffic.
A lot of the child sites for the smaller sites are never used.
As worded, these two points are contradicting each other.
The main sites are meant for questions about specific topic (e.g. Coffee, Gaming, etc.) and the meta sites are meant for questions about issues in the main site.
Most people come only for the questions about the specific topic of the site, and care less about the site itself.
Having them together will clutter the site with lots of things those people won't like, and they would likely not stay, resulting in a dead site.
There are a lot of questions on the child meta sites that are duplicates of questions on the main site.
No, there isn't. Meta and main site are entirely different things and you can’t find duplicate questions between them.
The child sites do not offer any reputation points and so the questions/answers cannot be taken seriously.
No, reputation is only a number of virtual Internet points, so don't take it seriously. People who love their community take each and every question seriously to develop a better community.
The main site would gain more traffic.
Yes, the main site gains more traffic, but that doesn't mean having them together. The entire main sites are focused on knowledge. People come here to share and gain knowledge. So that is why they gain more traffic.
Shadow's answer addresses this point nicely - why we don't mix them together.
A lot of the child sites for the smaller sites are never used.
No. SE gives them a chance to discuss about the main site, feature request, etc. to grow their community, so that is why meta exists.
Stack Exchange as a whole is built with organization in mind. We have different sites depending on the general topic of the question, and tags within those sites to further differentiate between smaller topics. Titles and tags can (and often should!) be edited to help users find questions.
Having per-site metas furthers this organization; it allows much easier differentiation between questions about the site's topic, and questions about the site itself. Your wording is a bit confusing. Assuming "main site" is referring to the parent of the child meta: As Shadow Wizard said, users visit, say, Stack Overflow to get answers to programming questions, not answers about how the site works. Meta questions are not relevant or helpful to most visitors of the site.
If you're using "main site" to refer to here, Meta Stack Exchange: You can read this question for much of the reasoning behind having separate meta sites (it's written specifically for Meta Stack Overflow but the concepts apply everywhere). Essentially, an active user on, say, Cooking SE wouldn't be concerned with a burnination request for a tag on Super User. Independent child metas allow issues specific to one site (such as burnination requests) to be grouped together.
To address your bullet points:
There are a lot of questions on the child meta sites that are duplicates of questions on the main site.
Once again, I'm not sure if "main site" means the parent site or MSE. If you mean the parent site, in my experience, this rarely happens, and when it does, the question is quickly closed and/or migrated to the child meta. If you mean MSE, these are called cross-site duplicates. There are requests to allow some form of closing or linking cross-site dups, but it's acceptable as the answers may be different on different sites, e.g. discussion of whether and when resource recommendations are on-topic may be different on Stack Overflow than on, say, Game Development SE (and it may not as I'm not very familiar with GameDev.SE, but there are other cases where discussing the same or a similar topic would be different for different communities).
The child sites do not offer any reputation points and so the questions/answers cannot be taken seriously.
Why does that mean they can't be taken seriously? If anything, it means users will browse Meta sites because they're concerned with helping the main site, not because they want reputation.
The main site would gain more traffic.
If you mean the parent sites: no, they really wouldn't. If you mean MSE: yes, it would gain more traffic if all meta questions from all meta sites were asked here, but only because all meta questions for all sites would be squashed into one giant meta site, which is not a good idea (see above reasoning).
A lot of the child sites for the smaller sites are never used.
Yes, for smaller sites, the meta sites are generally used much less often because there's simply not as much that needs to be discussed as in larger sites. There's no reason to pressure people into asking more meta questions.
