Im more interested in the Aura design history that could be relevant going forward
The most obvious and frequently used argument for playing the minimum number of cards is simple: some cards are better than others, some cards will be your best cards, and you dont want to reduce the frequency with which you draw those cards
Friendly to a card type This can involve a wide range of things where you either help that card type (making it cheaper to cast, enhancing it in some way, using it to generate an effect, etc.) or that card type helps you (you get rewarded for playing that card type, having a certain number on the battlefield or in your hand or in the graveyard grants abilities, you can sacrifice them as a resource, etc.) Friendly to artifacts Primary: White and blue Secondary: Red White and blue, as the colors of civilization, are both very friendly with artifacts
The media giants playing both sides of the field
The gift is usually just a card or a 1/1 token, but some of the more bombastic gifts include an 8/8 octopus with Octomancer or an entire friggin extra turn with Perch Protection