A good read on this topic is The Pursuit of Noninvasive Glucose: 'Hunting the Deceitful Turkey'.

The biggest problem is that they are racist. Optical blood sugar sensing devices were developed a decade ago. They were pretty accurate for pale white people, ballpark for most skin tones and don’t work at all for Black people. Good luck bringing that to market. Apple threw out the whole product and restarted with infrared.