It may be related to the ELf (English as a Lingua Franca) phenomenon; use of English as a common language between speakers who don't have it as their native language, because it is the simplest method of mutual understanding.
Or marketing budget reductions; one ad that is probably understandable in most countries.

Nice But, #10, You probably hit the nail on the head. If today's advertising gurus had been around when French was the FLF, undoubtedly we would be seeing ads using French for their mottos here.

Yes, mazgringo and Nicebut.
The word "chic" in the advert would make it a little more international!
chaco_flaco, #12, I would agree, but my U.S. unabridged dictionary says that "chic" has been accepted as an English word since around the 1850s.

It was bad enough when the Germans made up the 'English' word "Wellness" to describe their spa hotels. But today I saw Wellments in a restaurant bathroom. What's next? Wellity?

You see "wellness" all the time here (USA) now. Before you know it we'll be calling mobile phones handys.

Remember when Cartier used the slogan "Les must de Cartier" in English-language media? A slogan that was (perhaps) chic in French because of the English in it, then used in English media where it was chic because of the French, but assuredly comprehensible because of the Franglais.
Language-Mixing in French Print Advertising. Only the abstract is available for free.
The Use and Abuse of the English Language in German Advertising
From 1950 to 1980, the share of English slogans was negligibly low. Before 1950 the English language was represented in claims by merely 2%. In the fifties, the amount even decreased to approximately 0%. The share of 1% of English, which was used in slogans from 1950-1960, raised during the seventies up to a level of 3% and remained stable until 1980. Conspicuously, English claims have gained ground in German advertising from 1980 onwards very quickly. The amount increased up to 18% and after the year 2000 even to 30%