I was in a "crossover" period, and ran many A/C service calls on mine, with a milk crate strapped to the back of the seat, to put a can of Freon in. Tool belt on, refrigerant guages hooked to my belt, and away I went!
As I got into building PCs at the same time as Michael Dell (he did a little better with the business than I did), I started using the Seca to do computer service calls. I once delivered a complete PC system with tower, monitor, keyboard, mouse, and printer, all strapped to the back, and in my backpack. I had my software and tools in a Samsonite briefcase strapped to one side, sitting on the pillion peg.
That bike could have paid for itself in gas savings in under a year. It didn't have to; I made enough to pay cash for it by making 4 phone calls (commercial A/C equipment distributor, electrician, plumber, and crane), and supervising the installation of a cooling tower that took one work day with a 2-hour lunch break. Easiest bike purchase I ever made, and the only NEW "new" bike I've ever bought in 40+ years, 165 bikes total. The bike had 3 miles on it, but sat in the dealer's warehouse for 4 years. It had been ridden from the warehouse to the dealership, and back, then put away.
EDIT (boy, howdy, the memories are flooding back)
My buddy, Nacho (R.I.P.) liked it so much, he bought it's twin from the same shop. His was a dealer demo and had been overbored, so it was a bit zippier. Of course, since I weighed 100# less than him, I could still beat him...
For some reason, I sold it, but bought it back many years later. It was tired but still fairly nice. It just wasn't the same, so I donated it to a youth pastor who needed transportation.
Cool bikes, those 650 Secas...