From the book "For the benefit of many", p. 78:
Q: When you are teaching in English, why do you use Pali and Hindi words in your chanting and your discourses?
Goenkaji: Well, these words are so pleasant to me. Pali is the language of the Enlightened Person, and Hindi is my mother tongue. They also create a good vibration for the students to meditate in. In the English discourses I am cautious and try to use them as little as possible, but in the Hindi discourses Pali verses are very helpful. They give inspiration, and Pali becomes easy to understand for many Indian students after taking only a few courses.
However, even in the West old students keep telling me, "When you recite a Pali gatha [verse] we feel good vibrations." A new student may not agree with this; he or she might have aversion and think, "What is this chanting? Why is he disturbing me?" But slowly this person will start to understand the benefits.
Last time the ten discourses in English were recorded the Pali gathas were reduced to a minimum and afterwards there were complaints about this. We cannot please everybody, some will remain discontented. We have to serve as best as we can, and you have to serve as best you can as Dhamma servers.