Intel Core 2 starting their 64bit CPUs is 20 years old next year. Athlon 64 is over 20 years old... I wonder truly how many real computers and not just VMs there is left.
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
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.