Your entire comment is predicated on him being concerned about losing the laptop. Clearly he isn't. Clearly he's only concerned about losing the data. After all, a laptop can be replaced.
With that point of view your comment becomes rather less relevant.
I wouldn't suppose people would mug him for his data. But having got the laptop, the data may very well be trawled through for email addresses to spam, credit card numbers to defraud, salacious photographs for blackmail, etc. Someone who mugs you is extremely likely to pass the laptop to a fence, who will then make the most of it.
Yes, the data will get wiped and the laptop sold, but the data will also be mined to see if it's of value. I assume the author doesn't want someone going through their underwear draw.
In the UK computers must be recycled, but recycling companies are required by law to shred hard drives. It was extremely difficult to get them to save the magnets for a youth project robot building exercise.
With that point of view your comment becomes rather less relevant.