How to get more Google reviews without breaking Google’s policy
Most of the gap between businesses that get reviews and those that do not is timing and friction, not persuasion.
The Places API returns a maximum of five reviews per place, chosen by Google, with no pagination. It is a product decision, not a quota.
The Business Profile API returns everything, but only for locations you own and have verified, and behind an access request.
Caching, quota handling, rate limits, attribution requirements and display rules. The API call is the easy part.
Inside a product, across locations you own, or combined with other data. Not to put reviews on a website.
The detail is in the Google Reviews API guide and the five-review limit.