You can turn-around a A320/B738 in ~20 minutes (low cost carriers do that frequently), a A380 is really challenging to turn around in less than 1 hour. Furtherm

You can turn-around a A320/B738 in ~20 minutes (low cost carriers do that frequently), a A380 is really challenging to turn around in less than 1 hour. Furthermore, the A380 will need space of ~2 A320/B738. So per given space and time during peak hours, small planes can actually get you more capacity than large planes. You could change that (boarding A380 through 7 doors, probably faster refuelling) but planes like the A380/B747/B777 were never designed for quick turnarounds.