We stick to our local languages because they're part of who we are. Europe would probably have a little more money if we stopped doing that, but it would be a lot poorer.
Scandinavians are some of the most successful societies, despite of small languages. Languages have cultural baggage to them; every time I hear English, I see high inequality, poor worker rights, obsession with money, yet excellence in science and higher education. No one wants to abandon their own and assume English identity.
(A language is a dialect with an army and a navy)
https://en.wikipedia.org/wiki/A_language_is_a_dialect_with_a...
For a splendid example, see https://news.ycombinator.com/item?id=10220679.
Also one of the huge benefits of post WWII order was the creation of homogeneous national countries. Which explains the abnormally long peace period. So nationalism and national identity are extremely strong in europe.
England does not see itself as part of Europe. If anything, England sees Europe as an extension of France. And England hates France with a vengeance. Geography and history aside, the UK is not a European country at heart.
The challenge is that still a lot of things are distributed (you are vastly more likely to read your national news, shop at national ecommerce shop, shipping rates are much higher if you do that oversees, etc.).
Because the local language is a majority language where it is the local language, and, globally, every language is a minority language (and English isn't even the biggest minority -- its #2, far behind Mandarin, for total speakers, and #3, behind Spanish which is far behind Mandarin, for native speakers.)
Not all of us speak English.
Călătorie sprâncenată, frățâne!
Because they don't all know English and even if they did, why the fuck should they?
We Arabic speakers also enjoy or suffer , it depends on your perspective, from this phenomenon as we mostly speak in dialect all the time but in formal contexts esp. in writing, we use the Modern Standard Arabic instead. However, writing in dialect or MSA derived languages is becoming more acceptable in literature and the press at least where I come from, that's Egypt.
No wonder Jeb Bush is taking a lot of flack for speaking Spanish in public when you got crowd like this.