This psychological tactic works more often than not. Personally, I get tempted whenever I see wheels spinning or whenever I receive scratch cards with hidden rewards even though I know deep down that I probably will earn an insignificant amount.
This is why I usually try and avoid such stuff whenever possible in order to resist the temptations. Sadly, most gamblers cannot resist fall prey to such temptations.
Most of them don't realise that such games usually have the highest house edge when compared to games like Dice, Baccarat etc.
Of course it's all about psychology, but the important difference here is that Freebitcoin is provably fair. So yes, you do know that your chances are really low, but it's free. Better than any paid lottery out there IMO. And it takes only a few clicks to get the result. I've already won 5000 satoshi 2 or 3 times (which is $7 or more by the way).