Publishers are very selective about sending authors on tours, because (except for the very biggest names) tours don't make money and cost quite a lot to organize -- they're loss-leaders designed to generate enthusiasm among booksellers (independent bookstores generate disproportionately more sales than you might expect given their usually-small size, and an enthusiastic local seller who feels a sense of amity towards an author can over a period of years produce thousands of additional sales).

I got sent on a couple of book tours when my career was spiking, over a decade ago. Grueling, and no very visible short term impact on sales ... and that's with free ticketing (the events were to generate publicity, not revenue). Many authors are middle-aged introverts and don't really thrive under such conditions -- myself included.