the reason for not having clocks is simply to induce the players to forget time and not realise how late it is getting or how long they have spendt there. The longer the player stays the more money the casino makes.
The odds for each game are stacked in favor of the casino. This means that, the more you play, the more the math works against you, and the better the chances are of you walking out of the casino with less money in your wallet than when you came in.