This isn't just related to this forum specifically but in general related to all Q&A forums. A lot of questions often are not marked as 'Solved' because the person who asked the question doesn't really bother doing so - especially a common practice among newbie users who take to forums to get specific queries answered and don't look back.
Do the moderators on Salesforce StackExchange mark questions as solved in case there are legitimate answers and the person asking the questions doesn't do so? This is somewhat related but I believe there's no harm in giving credibility for answers where due.
This isn't about statistics but more about helping out others with answers which may already be there but haven't received blessings from whoever asked the questions (and the moderators).
Food for thought perhaps?