Ahem... I hate to break it to you... 10 isn't even the limit of allowable tags, it is just what Steempeak set their own limit at. I am not sure if the blockchain actually sets a limit, but if there is a limit, it is REALLY large - see e.g. https://steemit.com/revolution/@netuoso/jfk-secret-societies-1510793787

But back to the actual point at hand, I totally agree with you that if there isn't at least one relevant, popular tag to the post e.g. #art or #photography or whatever is appropriate, than something is wrong. And using tribe tags that aren't relevant is actually straight up harmful and likely to get you muted from the tribe's front end and your rewards flagged away anyway... so... why do it :)