Yeah, I would have prefered a cart to save memory space, too. But I also wanted the PS3-versions, which aren't included in the Vita-retail-trilogy, so I would have to buy both retail versions.
Vita retail 29 € + PS3 retail 23 € = 52 €
digital HD-trilogy (cross-buy) = 15 € (18 € / 6 x 5... I got 60 € PS Store credit for every 50 € I uploaded to the wallet)