[Question] Why have exposure notification apps been (mostly) discontinued?

I recently noticed that exposure notifications for COVID-19 in the app that I had been using, called CA Notify, had stopped working (I had attended an event a few days prior, and was feeling ever-so-slightly unwell, so I thought to check to see if there were any exposure notifications from the event; anyway it looks like my ever-so-slight not-feeling-well was unrelated to the event and it self-recovered quickly).

After digging further, I found that most of the COVID-19 contact tracing apps stopped sending exposure notifications around May 11, 2023, when the COVID-19 pandemic was officially declared over. See e.g. https://​​www.cnbc.com/​​2023/​​05/​​12/​​covid-most-americans-wont-receive-exposure-alerts-on-phones.html

I think this is a bit … sad? I feel like contact tracing /​ exposure notifications is one of the kinds of precautionary measures that provides benefits at ~0 personal cost, unlike things like social distancing, masking, and vaccinations. In fact I would have liked exposure notifications to be expanded beyond just COVID-19 to cover more respiratory diseases and also include the ability to report new ailments before they spread widely. Seems like keeping an exposure notification system going and having people regularly use it to report infections would be good practice for both known and unknown ailments.

I hope that companies and health institutions are secretly working on some more robust longer-term solution such as this, but have not seen any evidence of it so far.

What are the reasons this might have been shut down? I couldn’t find much discussion online, so I tried to come up with my own ideas, and here they are; I am not personally convinced of any of them:

  1. Maybe the cost of running the backends was very high for the institutions managing the app (the California government in case of CA Notify).

  2. Maybe people think “ignorance is bliss” when it comes to getting notified of COVID exposures, insofar as after having received such notifications, they may be morally obliged to cancel meetings with other people, incurring financial and social costs of doing so. They’d rather not be notified and incur the increased risk of transmitting COVID.

  3. Maybe the exposure notification system was considered a security risk or liability risk of some sort, so shutting it down was considered prudent as a way to reduce the risk of some major scandal. (I think, even if this is the case, it’s probably better to tweak and fix any such issues now than try to rush out another iteration during the next pandemic!)

  4. Maybe there’s evidence/​data that the exposure notifications system didn’t work at all? Or that not receiving an exposure notification gave people false confidence that they don’t have COVID?

NOTE: Originally posted to Facebook at https://​​www.facebook.com/​​vipulnaik.r/​​posts/​​pfbid02Q1jFK5LB7KhGWhj2rEteud8QfFrB2UxhyZYbWxQzSZWrpigJSasJEX7mVZKYmBZPl but I didn’t get responses on Facebook and I think LessWrong might be a better venue for discussing this.