I'm a little confused as to why all of the Stack Exchange sites are such narrow focused topics. Like if you have a question about a website or about buying phones, it quickly becomes off-topic in many of the Stack Exchange sites. It forces me either to find a different Stack Exchange site (at which I'll have no rep) or without a Stack Exchange site to go to (which is sad to me, because I LOVE the Stack Exchange format for any question that has a specific correct answer... at other forums or wiki's I find it annoying not to be able to vote people up or see the single accepted answer quickly).
What would be so wrong with having a "Science, Math, Technology, Philosophy, and Home Repair Overflow" site where nothing is "off-topic" (but things still would need a specific answer, so closing questions as "not a real question" or "subjective" is still necessary).
Isn't that what the tag system is for? There are plenty of ways at only looking for tags your interested in... and there may have to be categories of tags like mathoverflow so "python-programming" doesn't get mixed with "python-snakes". A lot of people work very hard to keep the Stack Exchange sites on topic, and I am just curious as to why? Why can't they be all together, just separated by tags?