Even if they gave a squat about which artists their music is played before or after, there isn't much they could actually do about it - and as was stated upthread, they got paid, so who really gives a darn in the end. Regarding touring with other artists, there are scores of books written about various bands and artists and they're filled with stories of squabbles, fights, breakups and the like, with drama occurring both between bandmates, and between various bands and artists that toured together. The Eagles' Don Henley and Glen Frey famously didn't get along at times, with Frey telling Henley one night that as soon as they played the last note of the show, he was going to beat the sh!+ out of him. Elton John and Billy Joel toured together on and off for about 16 years and made hoards of cash from one sold-out run after another, but their relationship was often strained with Elton fed up with Billy's drinking and vices, and Joel unhappy because he liked to improvise and toss random songs in when he performed, while John preferred to stick to the script and often uses the same set list and banter each night.