Not sure if some one already mentioned, these numbers are rarely for general public

1. These are core to the (service level agreements) SLA's for the enterprise companies when they evaluate and sign the contract (must for government RFPs)

2. The contracts generally have provisions for payback or penalties for missed SLAs

3. When your product depends on any of the products directly then the availability of your product has to take into account the availability of the dependent services. Eg, I can easily sell a SLA of two nines for my service if I am building it on a platform which has SLA of three nines, other way around is always questionable (though possible)

4. All of this is what used to happen may be up until 5 years ago. As of today even with good number of outages, company like AWS has not updated their availability to reflect those outages. Ideally all the companies built on top of AWS infrastructure would have to update their availabilities in a cascading manner but some how everyone decided to skip the beat

5. At this point, calculation of the availability itself has become so opaque that no one understands it anymore so no one questions it either