Usage policy is not necessarily metered vs free. It's a mixed bag of user expectations, developer needs and technical properties of the connection. Connections are by no means only unmetered broadband and metered LTE. I have recently experienced several connection "quirks" that require different approach:

  * punishingly high RTT
  * packet-per-timeframe ratelimit
  * throttling by queueing packets
  * unstability (some requests get served in tens of ms, others get lost in void)
  * connection jumping from one provider to another (e.g. mobile/wifi while next to home)

For example, jaggy GPRS in the middle of nowhere can mean two things: I working in a field and need to check something as quick as possible without ads and other unnecessary cruft hindering with that, or I am resting in a cabin and am willing to wait for a "proper" app to load.

I may also have two connections: fast metered, slow unmetered and would like applications to load important stuff fast over metered network and cosmetics over unmetered one. Too bad I have to pull whole javascript framework first in order to see anything, because web components, and it's uncacheable because it's webpacked with application code.