SS will do bends and curves. It won't easily do compound curves. I mean, seriously, look at most stainless steel appliances and grills. They mostly have some curves but a lot of bends across the whole sheet. It can easily be drilled, welded or brazed upon to affix fasteners. This isn't some mysteriously unknown material, it's commonly used everywhere. You probably have several examples of it within your view.
I believe Elon got enamored with Stainless Steel since they switched the Starship design to that material rather than advanced composites. When it came to the truck he had that in his mind as the most durable, cost-effective material (and he's probably right). The rest of the design sort of falls out of the directive to make the body out of stainless steel. Don't do a lot of complex compound curves. Don't paint it. Save manufacturing complexity by making the panels all stamped out and bent on metal brakes. They can probably produce many, many of those body panels in a fraction of the time that it would take to press normal body panels.
Nobody makes car panels out of stainless steel because they can't be bent into sexy car/truck shapes. If you simply eliminate the requirement of having curves and you're looking to save complexity you end up with a tessellated design like the Cybertruck. Then it's just a matter of having enough balls/foolishness to try to sell a vehicle like that to the public. We'll see in a few years if it was the right move. If it is, then Tesla will be legitimately able to sell more capable, tougher trucks than their competitors at a better price. Then those competitors will start copying the design and then it will become the norm (possibly).