> I still don’t understand this industry’s obsession with predefined fixed limits on unrelated resources.

1. It keeps their billing simpler. They would have to (or otherwise make it up elsewhere) charge different rates for different resources, making it relatively confusing + increasing support costs.

2. Much easier to forecast resources. If you know that you can fit X instances of type Y on a box, or W instances of type Z, it's easier to understand when/where you will need more hardware.

It's not perfect, I agree, but if an ad-hoc VPS product was profitable I'm sure we'd have seen it by now.