They claim it's to prevent bots, but we all know it'll soon become standard in every WAF out there (Cloudflare, Akamai, etc) to just blanket block browsers failing attestation.
All you need to know what will happen is to root an Android phone. You'd expect Netflix and bank apps and other highly sensitive apps to stop working. Okay, I can accept that, it kind of make sense. But the more you use the phone the more you realize a ton of apps also refuse to work. Zoom complains and marks your session as insecure, the Speedtest app refuses to test your speed, even the fucking weather app won't give you weather anymore. Jira/Confluence/Outlook/Teams also complain about it. It's ridiculous.
Even if it'd trust Google to not misuse the feature and genuinely use it to reduce ad fraud, the problem is the rest of the developers and companies. Those, they absolutely cannot be trusted to not abuse the feature to block everyone. Security "consultants" will start mandating its use to pass security audits, government websites will absolute use it, and before you know it, half the web refuses to work unless you use Chrome, Edge or Safari.