With all due respect to country singer-songwriter Roger Miller, Mike Watt is the true “king of the road.” In “What Drives Us,” the punk-rock vet talks about the lengths to which he’s gone to make a living as a musician — a pursuit that’s required him to get in a van and motor from one town to another, never sure of how many people might show at a concert or what he might encounter along the way. His balance from a 2019 trek, one of more than 100 tours the bassist has endured: 45 gigs, 45 days, 13,380 miles. The Minutemen cofounder sat behind the wheel for the entire trip.