Google announced on Wednesday that they will be removing Low Volume Keywords from the Search Terms reports within Google Ads.
The following announcement appeared within all of my accounts today:

What does this mean for Google Ads users?
Knowing the exact phrases that trigger your ads is vital for optimising your account – both in terms of finding additional converting keywords as well as irrelevant keywords that your ad is appearing for.
Personally, I check the Search Terms report at least once a week for each of my clients, more for the bigger and newer clients, finding negative keywords to prevent my clients appearing for in the future. It’s vital for limiting wasted spend.
The message within Google Ads states that only keywords that are searched by a “significant number of users”, meaning several low volume keywords won’t appear from now on.
Can I still see all of my Search Terms?
It appears that all of your search terms are still accessible by API and Analytics based on my clients’ data. How long this will last for remains to be seen.
Why have Google made this change?
My initial guess would be that this is another move from Google towards bidding on Audiences rather than words. it’s been over two years since AdWords became Ads after all.
Google has been in favour of machine learning and AI. Whilst their own system’s suggestions are improving, I am still yet to see a Responsive Search Ad convert better than an Expanded Text Ad, or straight up approve everything in the Recommendations tab for a single campaign. Perhaps one day Google will get it right, but for now, it simply appears to be another way for Google to make more money from their service, much like they did with the expansion of “close match variants” a while away.