Because no one looks at an Arduino or a Raspberry Pi and says, "I would pay top dollar for a version of this thing that has x86 instructions."
eg, https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=738575
Once you make your 'x86' incompatible enough that it won't actually run glibc fully, you've negated the whole point of having x86 in the first place.
Intel's "strategy" with Quark etc has been to to sell you on the idea of a ubiquitous platform, and then provide a niche platform that looks "mostly similar" to the ubiquity you were promised.