The issue of Google My Business (now Google Business Profile) reviews decreasing is a concern for many businesses, as reviews are critical for visibility, credibility, and customer trust. Here's an overview based on information available on the web:

Common Reasons for Decreasing Reviews:

Policy Violations:

Reviews might be removed if they violate Google's guidelines, such as containing spam, fake content, off-topic comments, profanity, harassment, or personal information. Google actively scans for and removes reviews that do not comply with these policies.
Algorithm Updates:
Google occasionally updates its algorithms to improve the quality of reviews, which might result in the temporary or permanent removal of reviews that are deemed less relevant or authentic.

User Actions:

If a user who left a review deletes their Google account or specifically removes their review, this will decrease the review count.

Technical Glitches:

Software bugs or issues with Google's systems can lead to reviews disappearing temporarily or permanently. This might include glitches where reviews are incorrectly flagged or not displayed.
Profile Merging or Updates:
When businesses merge profiles or change critical information like their address, there might be delays or issues in how reviews are reflected on the new or updated profile.

Review Filtering:

Google employs review filters to combat spam and maintain the authenticity of reviews. Sometimes, legitimate reviews might get caught in this filter due to various reasons like suspected duplicate reviews or reviews from the same IP address.

What to Do:
Contact Google Support: If you believe reviews have been removed without a clear reason, you can reach out to Google's support team for clarification or to appeal the removal.
Check Compliance: Ensure all reviews on your profile comply with Google's review policies. Educate your customers on these policies to avoid unintentional violations.
Gather Evidence: If possible, document missing reviews with screenshots or other proofs. This can be useful when discussing the issue with Google support.
Encourage New Reviews: While you address the issue of missing reviews, continue to encourage new, genuine reviews from satisfied customers. This not only helps maintain your rating but can also mitigate the impact of lost reviews.
Monitor Your Profile: Regularly check your Google Business Profile for any changes or updates. Quick action can sometimes prevent or resolve issues with review visibility.
Diversify Review Platforms: Don't rely solely on Google for reviews. Encourage feedback on other platforms like Yelp, TripAdvisor, or industry-specific review sites to spread your online reputation across multiple channels.

Recent Observations:
Recent posts on social media and community forums indicate that some businesses have noticed a decrease in their Google Business Profile review counts, with some attributing this to possible bugs or algorithm changes. However, these observations should be treated as anecdotal until confirmed by Google or through official channels.

Given the complexity of Google's system for managing reviews, it's essential to approach any decrease in reviews systematically, combining immediate action with long-term strategies for reputation management.