The staffing problems are not just in the transportation industry. I'm sitting in a food service establishment having a coffee waiting for my wife, and found the place to be ridiculously understaffed, even for the light mid afternoon crowd. Because I have a family member who worked in this industry, I have an idea about why they're having trouble with hiring people - the pay is lousy, no benefits, and they don't even guarantee you a set number of working hours. This has been going on for years, I guess the pandemic was the straw that broke the camel's back.
Amtrak must be different, as they're offering real jobs with decent pay, benefits, and guaranteed work hours. From comments made by Jim Matthews on the RPA blog, it sound like Amtrak management goofed when they encouraged early retirement at the height if the pandemic. The furloughs didn't help, either. Ince you lose experienced people, it's hard to get them back.