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A question of curiosity - why do we even need flavors?

I do realise that we need a way to provide instance configuration, but why
use such a rigid construction? Wouldn't it be more flexible to provide
instance configuration as a set of parameters(metadata), and if you need
some presets - well, use a preconfigured set of them as a flavor in your
front-end(web/CLI client parameters)?

Suppose commercial customer has an instance with high storage IO load.
Currently they have only one option - upsize instance to a flavor that
provides higher IOPS. But ususally provider has a limited amount of flavors
for purchase, and they upscale everything for a price. So instead of paying
only for IOPS customers are pushed to pay for whole package. This is good
from revenue point of view, but bad for customer's bank account and
marketing(i.e. product architecure limits).
This applies to every resource - vCPU, RAM, storage, networking, etc -
everything is controlled by flavor.

This concept has never been questioned anywhere I can search, so I have a
feeling I'm missing something big here. Maybe other ways are too
complicated to implement?

So does anyone has any idea - why such rigid approach as flavors instead of
something more flexible?
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