The other issue, one that varies from band to band due to financial circumstances, is the cost of touring. Yes, a top concert draw like the Grateful Dead probably made enough money from touring to sustain more touring, but on the other hand they had a lot more equipment to transport. In reading Rock Scully's book, his account of the European tour was a logistical nightmare, and the whole thing either had to come out of the band's pocket, or the record label's if the record label happened to provide tour support. Most independent labels don't, and even major labels probably don't do it for every artist. When they do, you can bet that the cost is recouped from the artist's future profits so it eventually comes out the artist's pocket anyway.
When Pink Floyd performed the Wall live, they only performed it four times and lost a ton of money. Although that was a huge theatrical production. But after Roger Waters left the band and the remaining members hired Rick Wright back into the band to tour, he was hired on a salary basis and not a percentage of profit. On their first tour, they lost so much money that Wright was the only one that made any profit because he was guaranteed a flat rate. That was a band as big as Pink Floyd, losing money on a tour. Some of the bands I've worked with - local/regional bands with no label support - can't afford to go more than 3 or 4 hours from home, and it's rare that they go that far. It's not really that they don't want to; if they could go further they would because there would be much better opportunities for them. Sometimes it's a tough choice for a band when something as wonderful as music comes down to what you can afford financially, and how practical it is.