Most, if not all of the Minor Gifts give excellent Roleplay hooks that can inform a character. Delaying the choice to take one (and again, this is only for the Minor Gifts) until a later level would allow a characters' development to inform that choice, rather than have to do so and effectively 'plan' that aspect in advance.
Level 10, 15, or 20 seem good, arbitrary places to be able, if a player chooses, to delay choosing something like Gift of Tongues or Greenthumb based on what their character does or who they meet during the early parts of their career.