Huge numbers of people who aren't native anglophones - certainly those working in some sectors and global organisations demonstrably do learn English, it's not an unfounded assumption. They may learn other languages as well but have you ever been in a meeting with colleagues from Japan, Korea, India, Germany, France, Russia, Bulgaria, China ... etc which was conducted in anything other than English?
Yes, many times. I've even worked in companies in London where the language of the company wasn't English and some meetings and almost all documentation was in French. I've had similar experiences having to use German in London. This is in Financial Services. I've lived and worked in Paris and chaired meetings in French, trained people in French, written documents in French, presented to clients in French and even done some fairly technical interviews in French (so technical that my French colleagues didn't even know the French terms for what I was presenting so we had to settle on using the English with a French accent). Note I wasn't hired for my language skills, I was hired for my business experience but having a second language has opened many extra doors for me.
I'm 100% English. Boringly so actually as there isn't even a hint of anything other than English in my background/family going back several centuries. (No chance of another passport for me post-Brexit grr). I started French at secondary school (a fairly rough comprehensive, definitely not private), did A level, did Economics and French at uni, went into Financial Services. I've used my French throughout my career pretty much. French/Swiss colleagues are usually delighted that I can speak French and always express their surprise (what a truly appalling reputation us Brits have for languages!) I also speak some Spanish, Italian, German and Cantonese (I lived and worked in Hong Kong for a few years - where I also spoke some French as there are a lot of French derivatives traders there) and I've used all of them in a work context although only for more simple things. It is always well received.
My current employer is a big name global financial institution. Almost everyone I work with speaks multiple languages. It's very much the norm in my industry. It's rare to have a week when I only speak or hear English. It's not just the language skills but also having an understanding some of the cultural differences that can really make a difference.
I think it's incredibly sad that people just don't want to learn languages these days (as is evidenced by the majority of posters on this thread saying not to bother). There's so much to be gained, much more than just the knowledge of another language.