Just an add-on... what about acts or artists you regret not going to see when you could have done...?
Black Sabbath ('78 iirc) cancelled their show one time when I was standing in the foyer waiting to get in (I saw them with Ozzy and RJD prior and post this point)... "Sound issues" was the official reason... the strong rumour was having trouble following their support - Van Halen, on their first UK tour... never did see them...
I gave away tickets to see Ozzys first solo tour as it turned out to be a friends 21st... never did get to see Randy...
Deeply regret never having seen Status Quo, although I had countless chances... never seen...
Grand Funk played London in '74, 2 months before I discovered them... never seen...
Black Oak Arkansas played a post Reading mini tour, one in London, one in Glasgow... I was in Scotland when they played London and back home for the Scottish gig... people really hated this band but I loved them... never seen...