Earlier quoted context omitted.
It's because for an international company there is really no clear cut way to say what is tax evasion and what is not. If your company is incorporated in France, has offices in Ireland and serves customers all over the world, how do you calculate where to pay what? Sovereign countries are free to set their tax rate to 0 in order to attract companies there.
I'm pretty sure Google does not have a problem figuring out that the source of it's profits are not occuring in Ireland.
How do you tax a German company paying an Irish company to show ads in France?