Not being under any obligation doesn't mean it is not a sensible a courteous way to do. You like it or not, english has become a defacto common international language.
While I speak 5 languages and try to learn some basic words of the local languages of any country I visit out of courtesy (how to say hello, bye, thank you, ask where are the toilets, etc), I wouldn't expect any traveller to know enough to understand this kind of specificities in any country they visit.
Near international airports and capitals usually yes you can usually get help in english accross europe, at least enough to get basic help and instructions.
While I speak 5 languages and try to learn some basic words of the local languages of any country I visit out of courtesy (how to say hello, bye, thank you, ask where are the toilets, etc), I wouldn't expect any traveller to know enough to understand this kind of specificities in any country they visit.