Is this comment based on the assumption that because users do not pay for most of Google's services, they should have zero expectations about the availability and longevity of said service? If so, let me approach this from the reverse:

A company creates a service to generate revenue. Google provides numerous free services from which they show advertisements (or crowdsource free labor such as the google voice training system or google image search tagging "game") to generate revenue. Another company might charge for said service but not flood me with advertisements. Both companies make revenue from their service offering.

Why is it okay for Google to shutdown services (which either served their purpose or weren't profitable) but so unspeakable if another company were to do the same for a paid service?

Regardless if you agree with that viewpoint or not, at the end of the day, Google has a long history of creating products, gaining users, and shutting down those products. This history has made it extremely difficult for them to break into a market such as this one because quite frankly nobody trusts that the product will be around very long. The utter lack of customer service also makes it difficult to place faith in their systems.

I've found Amazon's freely available reviews to be an extraordinary resource over the years. I use them regularly when researching something I want to buy, due to the sheer scale of their retail operation there are almost always tons of reviews. People may take the accessibility of reviews for granted, but it's still a great free service.

Amazon also previously had a free consumer-facing search engine, A9; along with a free maps / street view service.

At various times Amazon has experimented with free shipping, including in general in the past, or with a free prime trial, or their free super saver shipping program. Obviously these are incentive based systems that require a purchase to use, but the shipping is still free non-the-less.

They provide, if I recall correctly, around 5gb of free cloud storage for you to upload content to, with an Amazon account.

They provide their Kindle book software across almost every platform at no cost.