The algorithm is only as good as your data
When your ad platform sees incomplete or low-quality conversion data, it can't find your best customers. It just spends more to find worse ones, and you pay for the difference.
Missed conversions

30 to 40% of conversions never make it back
Browser pixels are blocked by ad blockers and iOS before they fire. The conversions happen, but Meta and Google never hear about them, so they optimize as if they didn't.
Thin event data

Low event match quality scores
Pixels send thin event data: maybe an email, maybe not. Low match quality means the platform can't tie conversions to users, so attribution and targeting both degrade.
Poor targeting

Weak lookalike and broad audiences
Seed audiences built on partial data produce weak lookalikes. As the platform expands them, the quality degrades further, and your cost per quality conversion climbs.