People also use it to determine their individual luck.  If you've found 5 blocks total, and have a total payout of 140 btc then your more profitable than you would be solo mining, hence lucky. 

However if you have found 5 blocks total but have only been paid out 100 btc, then you're less profitable than you would have been solo mining, hence unlucky.

This is all assuming you only mined after the block halving.

Personally, I've found 7 blocks, and have been paid out 468 btc.  So I'm well ahead of the game (95% of those stats were earned pre-block halving so my blocks count as 50 btc).