CBP Reminds Travelers to Allow 72 Hours for ESTA. Why?

ESTA website has this alert on top in red.
REMINDER: Apply for ESTA no later than 72 hours before departing for the United States. Real-time approvals will no longer be available and arriving at the airport without a previously approved ESTA will likely result in being denied boarding.
Why is that so? ESTA approval previously used to be granted within minutes if not seconds. Is this a generic statement or a policy change?
This press release does confirm the policy change but does not list any reason as to why this was changed.
Due to changes in ESTA application processing, real-time approvals will no longer be available. Citizens of participating Visa Waiver Program (VWP) countries traveling to the United States are strongly encouraged to apply for an ESTA at the time of booking their trip and no later than 72 hours prior to departure. Applicants who apply on the same day of their flight’s departure risk not having an approved ESTA prior to their scheduled departure. International travelers without an approved ESTA will not be authorized to board their flight.
(the emphasis is mine)
Best Answer
Not an official reason but I've had an ESTA delayed because of payment difficulties. I'd used the same card to pay for a plane ticket, a seat upgrade and an ESTA in rapid succession, all to US companies; my bank flagged that as potential fraud and refused the ESTA payment. The next morning, I got an email from CBP saying that I couldn't have my ESTA until I'd paid for it.
So it certainly seems prudent for CBP to recommend that people don't apply right at the last minute. Even completely routine applications can get delayed. As far as I recall, CBP have always advised people to apply at least 72 hours in advance of their planned travel.
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Why is my ESTA taking 72 hours?
Why is your ESTA application pending for up to 72 hours? ESTA applications can typically be flagged for additional security checks. A pending ESTA application signifies that additional screening is needed to process your application and ensure you do not pose a security or immigration risk.Can I travel to the US with less than 30 days on my ESTA?
Your ESTA authorisation needs to be valid for when you enter the U.S. and will allow you to stay within U.S. territory for up to 90 days from when you land. Therefore, it is okay if your ESTA does not remain not valid throughout your stay in the United States as long as you do not overstay the limit of 90 days.How long do I have to leave the US before I can return ESTA?
Therefore, the length of time of your total stay, including the short trip, must be 90 days or less.Can an ESTA be approved in 24 hours?
We accept your ESTA application at anytime, 24 hours/day, 365 days/year. The results of your application should be sent about three days after you apply, but we recommend applying for ESTA soon after you decide to travel to the U.S.ESTA Explained
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