There is strong variability across Amazon/Facebook accounts.
For example, some agencies use Zontracker and even with similar methods have little tracking in one account and amazing results in another.
Many users are having phenomenal results with Zontracker. However, some users are skeptical and try one account before activating it on multiple accounts. They don't see results and never activate the other accounts. Huge missed opportunity.
Every account is very different. We haven't figured out why but it's likely the nature of differences in the brands, products, audiences, ad strategies, matching effectiveness across different regions depending on reliability and accurateness of customer names/addresses/etc, and tech effects on privacy and the way data is processed.
Some brands have completely switched their advertising and marketing strategies with big effects on the tracking quality. Try it for yourself, mix it up, and see what data you get.