The problem is that because all items, including extra lives, regenerate when you die. Therefore it is relatively easy to get inifinite points just by dying, grabbing a 1up, dying again, et cetera. Even if there is no 1up hidden in the level there is often at least one regenerating item you can use to accumulate a lot of points without effort. It is way more of a challenge to score as least points as possible, or complete a level within a certain time limit.

This thread might be interesting: http://jazz2online.com/jcf/showthread.php?t=15528