I doubt that i386 is still widely used. You are more likely to find embedded ARM32 devices running Linux, for x86 this is only the case in the retro computing community.
One notable use case is Steam and running games under Wine -- there are apparently a lot of 32 bit games, including still some relatively recent releases.
Of course if your main use case for the architecture is "run legacy binaries" then an ABI change is probably inducing more pain than it seeks to solve, hence the exception of it from Debian's transition here.
Plus, keeping i386 the same also means any still available support for running 32 bit binaries on 64 bit machines.
All of these cases (especially the installable 32 bit support) must be as big or bigger than the amount of ARM machines out there.
Note also that the numbers are log-scale, so while it looks like Arm64 is a close third over all bitwidths, it isn't.
Also, I’m sorry to have to tell you that the 80386 came out in 1985 (with the Compaq Deskpro 386 releasing in 1986) and the Pentium Pro in 1995. That is, i686 is three times closer to i386 than it is to now.
People still buy 16-bit i8086 and i80186 microprocessors too. Particularly for applications like defense, aerospace, and other critical systems where they need predictable timing, radiation hardening, and don't have the resources to get new designs verified. https://www.digikey.at/en/products/detail/rochester-electron...
Linux is a lot more uniform in its software, but when emulating windows software you can't discount i386