Keep in mind that the Psion starts out with only 3 powers, and the Wilder starts out with only 1. It is easier to keep track of X or Y or Z than it would be to keep track of "3 0th level spells" in one category and "1 1st level spell" in the other category (barring ability scores adding some slots here), since that is 4 things rather than 3 things. Plus the character has to pick them out at the beginning of every day, if a Wizard or Cleric or Druid. If you have not had to suffer through a slow player deciding whether to switch out their spells, and for what, every damned day, then you have been more fortunate than I.