I work with quite a few people who "need" to print things every day.
First of all, the vast majority of things they print don't require printing in the first place. As an almost stereotypical example, we have one lady who:
I think it helps to be cognizant of the fact that many of the older folks have more experience than you do, and that those experiences are probably more diverse.
Maybe you are too young to be aware of this or maybe your work doesn't involve it, but in the 80's and 90's, many businesses required their workers to save all paper invoices going back 10 years for audit, in chronological order. Electronic records were not acceptable because of formatting and technology changes over time (no PDF) and because often information was communicated via fax or physical mail, and it was easier to print than to digitize/OCR. Where I work, we only fully got rid of the fax machine this year, but it can still cause a problem when interfacing with less e-friendly companies, like smaller machine shops.
Regarding trusting computers, it is also much easier for a careless worker to catastrophically delete ALL electronic invoices with a single keystroke (what backups? I needed a spare hard drives for something else!) than to accidentally burn 4 filing cabinets worth of paper.
So make fun of the baby boomers if you like for being more hesitant to shift to contemporary practices, but remember that they probably make fun of millennials for only being able to focus on tasks for 5 minutes at a time, not being able to spell without a spellcheck, having poor reading comprehension, and not being able to work more than 40 hours a week without massive complaints! (Yes, these are all the complaints that I hear.)