I think any artist who has had even minimal success has to play "the hits" and/or more popular tracks because those are the ones the audience loves.
Go to any concert and they applaud the most familiar wildly and give "polite" applause to the lesser known one's.
Which I think is completely rude.
In Gord's case,if he didn't sing those 5 major U.S. hits out of the 6 that he had,some folks would start shouting those titles out anyway. So better he just sings them.
He most likely hasn't done "The Circle Is Small (I.C.S.I.I.Y.E.)" for a long time,which was his last top 40 hit.
Yopu never know though,he could throw something obscure in anytime,as long as he and the guys have rehearsed.