Why does Google ask for a CAPTCHA when using ExpressVPN?

When using ExpressVPN, or any VPN for that matter, Google often prompts a CAPTCHA because it detects irregular traffic patterns which can resemble automated bots or malicious activity. VPNs mask the user's IP address and allow them to share IPs with many other users. When multiple requests come from the same IP address within a short period, this triggers Google's security protocols since it deviates from typical human behavior where each user generally has a unique IP. The CAPTCHA serves as a verification method to ensure that the entity attempting to access the service is a human and not an automated system that could potentially be involved in spamming or distributed denial-of-service (DDoS) attacks. By solving a CAPTCHA, a user proves their authenticity and is allowed to proceed with their search or other Google-related activities.