Have you noticed that on the new $10 Black game, the instant winners are all symbols, a departure from all current $10 and $20 instant winners? Frankly, I think it's much easier to spot 50, 75, 100, and 500 than symbols that you match on the card description.
I have degrees in Economics and Psychology, so the lottery intrigues me from two different perspectives, the mathematical/statistical and phychological aspect. With psychology, it's both how they design the game to entice players and also perception in indentifying winners. Like Jon D mentions above, it's not accidental that large prize winners might be the last spot or with the next $10 game, have symbols for instant wins, when $10 and $20 players are conditioned on seeing numbers for instant wins.
We know that you don't have "x chances to win" that we see adverstised on tickets. It's all predetermined, you're either a winner or not on each ticket but that plays to the psyche of the average player. The ticket itself has the 1 in x odds of winning a prize.
Also, CAScratcher mentioned that losing tickets have two top prizes in the prize field. I see that too. And, some of those matching numbers might be off by one from winning numbers to cause some people to think they "almost" won the top tier prize when that's not the case. Very sneaky.