Here is why those tags are there. It is because of taxes. They show tax has been paid on the product from the manufacturer. Once an individual has purchased the product, you are free to remove the tag. You will not be penalized. I managed a furniture store, that's how I know.

Yes, I was too. I still don't know what to do with them.

well yeah, it says "under penalty of law"

That does not apply to the purchaser/owner.
The tags give information about the furniture (applies to chairs and couches as well).
If you pulled the tag off in the store, you'd have to buy it...but once you've already bought it you can do what you want with the tag.

I never thought of it

Never had the inclination quite frankly, but if I had, I'd have claimed "illiteracy."