the infographic choice of countries to decide the number of people isn't really correct. There may be more french speakers outside of france than in france itself.
Speaking more languages makes you more cultured because it lets you interact more easily with that culture, e.g. over the internet and so you learn new stuff.
If I didn't know english I'd know nothing about how americans think, dubbed hollywood movies just let a limited amount of knowledge through.
Since english is an international language, it gives you more access to foreign culture than other languages, but the vast majority of english cultural content on the internet is still anglo-saxon-dominated.
People should learn languages because I don't know how they would fill all those hours in high school if they didn't teach any language.
It's tourists who have to know the local language or at least english, not the other way round. If they don't even know english or at least french/german and broken english, people get frustrated fast.
Saying "You're in America. Speak English!" is arrogant only because tourists should be welcomed since they bring economic activity to the area. Expecting a tourist in america to know at least broken english isn't too much. You should not give them a hard time over it though.