The difficulty is that questions that solicit opinion based answers often become unnaturally popular and difficult to moderate. Consider https://stackoverflow.

The difficulty is that questions that solicit opinion based answers often become unnaturally popular and difficult to moderate. Consider https://stackoverflow.com/questions/84556/whats-your-favorite-programmer-cartoon https://stackoverflow.com/questions/84556/whats-your-favorit... and the "is another answer going to be useful?" Or https://stackoverflow.com/questions/1711/what-is-the-single-most-influential-book-every-programmer-should-read https://stackoverflow.com/questions/1711/what-is-the-single-... The "no opinion based questions" is a clear line that can be drawn (rather than other squiggly lines that are more difficult) that reduces the overall moderation workload. You'll note that https://mathoverflow.net https://mathoverflow.net allows such questions - but they have many fewer questions per day and a much higher percent of the userbase performs moderation actions. This means that you can allow for that additional workload (which is a few questions rather than hundreds or thousands) to be spread across a larger part of the site's users. If you want Stack Overflow to allow such questions, then get 1% of the user base to close questions that should be closed every day so that the moderation tasks on them don't get too heavy on too small a group of people who would eventually say "we're not carefully moderating this anymore and instead not allowing those questions at all."