Lost Market

A working Apple Watch on an ink-free wrist (Getty Images)

The Apple Watch doesn't work on some people with wrist tattoos.

Apple uses various spectrums of light to track the blood flow through your skin. Anything that reduces that light's reflectiveness — ink pigmentation within your skin, for example — can interfere with that sensor.

For those wondering: natural skin pigmentation doesn't block light the same way artificial ink pigment or even scar tissue does, so you shouldn't run into a problem if your skin is naturally darker.

Inference: very few, if any, Apple testers have wrist tattoos.

Another explanation: Apple may have concluded that only a small proportion of 45 million tattooed Americans would have sensor-interfering ink in the watch-wearing area, not enough of a lost market to delay release.