Because the levels of radiation are less than what you'd find in just about... anything around you. We're talking mBq per liter.
If you eat a single banana, you'd get more radiation exposure than if you chugged enough of this wine to give you alcohol poisoning.
Also, please, keep in mind that Radiation and Radioactive Particulate are different things. You can't really "put radiation" in anything, any more than you can "put light" in anything - most radiation we interact with *is* light, after all, and little of it lasts more than a few milliseconds.
Radioactive particulate is a different matter; it emits radiation.
Still, we are talking mBq/Liter. You might as well measure a beach by milli-granules-of-sand. Becquerels are not often used in professional communities regarding radiation because you wind up with measures on the orders of "Hundreds of Thousands of Becquerels" without it meaning * a dang thing *.
More common is the Curie.