Important sentence is "..or at least not as often as they should" :)

I have no doubt most people brush their teeth in one capacity or another, but do you really think 98% of people brush them regularly and sufficiently? I reckon that drops down quite a few double digits at that point, and since we're talking about populations here that's quite a lot of people.

If that figure is for the US, then that's ~7M people. Feels like "many" to me.

2% is definitely many