I suspect the number would be quite a bit larger. You have to consider how many with diabetes would be willing to wear contact lenses, and if you consider what the tradeoffs involved are, I think you'd find it's a rather large proportion.

Managing blood sugar how we do it now is a far larger bother than wearing contact lenses. I would guess that most diabetics who could afford them and did not have some physical aversion would use the lens monitors.

The alternative is primarily: draw blood from your finger every time you want to know where your blood sugar is. (There are other 'continuous' glucose monitors, but you have to keep a needle in you all day, and my understanding is they are inaccurate enough that you still often need to check sugar by drawing blood.)