Why do cars in Scotland often have stickers with the name 'Ecosse'?

In the United Kingdom imitation international codes are sometimes seen for the various parts of the country. For example, in Scotland oval stickers with "Ecosse" or "Alba" (Scotland in French and Gaelic respectively) are occasionally seen on cars.

https://en.wikipedia.org/wiki/Vehicle_registration_plate

Gaelic I can understand, but why in French?

Scotland's main foreign language is French. The special relationship between Scotland and France, acknowledged in the phrase 'The Auld Alliance', has formed a bond between the two peoples that survives irritations and misunderstandings. The Scots helped France and the French helped the Scots. Though this does NOT answer the question directly, it would seem to have a bearing.

http://www.electricscotland.com/france/auld_alliance.htm
https://en.wikipedia.org/wiki/Auld_alliance
https://en.wikipedia.org/wiki/Languages_of_Scotland

Also, Mary, Queen of Scots was brought up by the French Royal family and she married the French Prince or Dauphin, Francis, when she was fifteen. When Francis became King, she also became Queen of France. Francis however died from an ear infection the following year. Mary was no longer Queen of France and she returned to rule Scotland.

http://www.bbc.co.uk/scotland/education/as/burghlife/page.shtml?page=mary

In practice, the Auld Alliance is a relative of the glorious clannery of the Victorian period. The French wanted to keep the English occupied so they allied with the Scots. And the Scots usually got hammered. The Scots go on about the Auld Alliance; the French mostly don't know what you're talking about. Part of the reason for 'Ecosse' is that at least all the French, half the Belgians and quite a few of the English will know what it means. 'Alba'? The English won't know what it means, and the French might think of l'Albion perfide (Napoleon's phrase). The fact that the first 14 pages of Google links for "Albion perfide" are in English (OK, one in French and one in Czech) indicates that the French do not, as the English fondly and proudly imagine, use this term all the time doesn't really come into it. Gaelic hasn't been used in the main part of Scotland since well before the 'Auld Alliance" started - if it ever was. A relation of British and Welsh was spoken in Strathclyde. A relation of English - Scots - was the language of the part of the country that mattered at the time that mattered - the Lowlands and Borders. https://en.wikipedia.org/wiki/Auld_alliance et al
Baloo has Highland ancestry, and is also descended from the Black Stewarts of Paisley, who didn't get hung for sheep-stealing. This fact was noted in the family so they probably should have been.....