The problem is that the vendor is incentivized to publicly use whatever metric shows the highest availability. Otherwise, the vendor will have to pay back credits. The vendor's nines are never my nines.
The only way this gets solved is through cloud consumers providing streams of telemetry (sanitized of any data of value besides success/failure metrics of the underlying cloud primitives) to a central reporting uptime stats broker (Speedtest.net meets DataDog meets the Internet Weather Map). The incentives to fudge or exaggerate you uptime claims as a vendor through sales and marketing is too high; let the data speak for itself.
Do you trust AWS' status page? Or are you coming to Hacker News to ask why your network latency between instances has skyrocketed unexpectedly?
No, the vendor is incentived to provide a good experience to the customer, especially vendors that aren't AWS. They know they have everything to lose from customers changing clouds.
Ineptitude, and it being a hard problem, are sufficient to explain the status quo.