Mostly because they never consider the speaker human enough in the first place so no efforts were necessary to learn their language even though you spent time in that country. It's much easier to laugh at the poor locals who try to do business with you in their limited English.
Again, exceptions depend on your racial preferences. If it's that beautiful Castilian girl you met in Barcelona, Spain and hear her speak only Spanish, you will want her to speak indefinitely even though you don't understand a word of Spanish.
However, if it's Juarez from Mexico, Cuan from Brazil or Pierre from Cameroon speaking Spanish, Portuguese or French respectively, they're nothing but monkeyspeak.
Pakistani/Indian: Kya main aapse akeley mein kuch baat kar sakta hoon? (Can I speak to you alone?)
English speaker: No monkeyspeak, Abdul. Say what you want in English.
Chinese speaker:(Where did you go for dinner yesterday?
English speaker: Whatever the fuck you meant in monkeyspeak!!!
Kulạ seneng kepanggih
kaliyan panjengan!! (pleased to meet you)
American tourist: Speak in English, Gook baboon. I don't understand monkeyspeak.