You mean like the scheduled LA6, LA7, LA8, Chicago 6 arena shows in 2015 that didn't happen because of the lack of demand? Plus Stockholm 4 was half empty since locals weren't interested.
U2 are a band that consistently tours and releases new music. Garth Brooks is not. U2 have been playing Chicago and LA on average every 3 to 4 years for 35 years since 1981. It would be unusual for there not to be an occasional dip in demand with such touring. Garth by contrast is only on his 5th tour in his entire career which includes a 16 year break since the end of his 4th tour. U2 has a real worldwide audience, unlike Garth and is not overly dependent on one country for 90% of their business. So I'd say selectively cherry picking a couple of cities from one tour is irrelevant, and meaningless, especially with this comparison.
U2 cannot do 300-400 arena shows in the US over a 4 year period, even with Bono in perfect shape/health. Garth is doing 19 arenas in prairie Canada, and there's probably 4-5 more in Calgary. Most U2 did was 3 stadiums in 1997 and 2 in 2011.
There is a way U2 could do that, plus Garths numbers would not be what they are if this was not only his 5th tour and first tour in 16 years. Plus U2 does not have to rely on the United States and can utilize the world for a 100 shows per year if they so desired.
Wow, Prairie Canada, I forgot that alone defines who the big touring names in the business are. What are Garth Brooks career totals for France? Italy? Germany? Spain? Netherlands? Belgium? Poland? Russia? Turkey? Israel? South Africa? Croatia? Sweden? Brazil? Argentina? Chile? New Zealand? Australia? Japan? Mexico?
Eagles/Metallica/Cher/Roger Waters have tours that push 4 years that are acknowledged within the biz.
3 at most with Metallica and Roger, and still, its not the standard.
U2 aren't completely precious about the newest album if gigs near the end of 360 only had 3 songs from Horizon. I smirk at you defending u2's album integrity the same week of onsales for the JT30 nostalgia tour. BTW, Garth is only doing 2 songs a night from his newest disc.
Most 360 shows played a lot more than 3 songs from the album, plus most fans purchased tickets expecting a show supporting the album, like the Rose Bowl show. The tickets were purchased well in advance with fans expecting the normal setlist make up from the new album.
For the first time ever in U2's 40 year career, they decide to do a selection of shows celebrating the Joshua Tree, yes a bit of Nostalgia. But are they milking it? Nope. They could ride a full scale Joshua Tree tour to numbers no one in the industry has ever seen before but their not.
U2 has a broad number of options for touring if breaking tour records were the only desire. Garth Brooks path to any sort of global record is far more narrow.
U2 will keep their highest grossing tour record, perhaps forever, while Garth is on pace for most attended tour of all time.
Again, the only way Garth is getting any sort of record is by grossly extending the tour far beyond anything that would be considered normal. What your missing is that other artist, if they so desired, could extend their tours beyond normal lengths as well. U2 could do that and they have far more places they can choose to play around the world than Garth does.