We're used to every new iteration of iOS breaking adoption records left and right within its first few days of availability, compared to its predecessors. However, it looks like iOS 15 this year is breaking away from that trend. According to a new report from Mixpanel, iOS 15 adoption as of Wednesday at 12 AM Eastern stood at just 8.5%. To put things in perspective, at the same moment in iOS 14's release cycle, it was already running on 14.5% of eligible devices. That's a pretty staggering difference, and points towards people not really being very excited about iOS 15 - thus not jumping...
Source: https://www.gsmarena.com/people_are_less_interested_in_ios_15_than_they_were_in_ios_14_based_on_installs_so_far-news-51087.php