His response:
Dad,
This is a carryover from the days before surface mount technology, when computer hacking required the use of a soldering iron.The jumpsuit protected the “hacker’s” body from stray molten solder. The balaclava, which you’ll note covers the nose and mouth, protected the individual’s lungs from harmful fumes that can be released during soldering, including lead, arsenic, organobromides and resin acid particulates. Some of these gases can also cause contact dermatitis, a risk that is also abated by the jumpsuit.
Of course, modern-day hackers can simply exploit operating system design flaws to perform their work. The dress is now ceremonial, though its use is required in the EU (some laws are slow to change!)
Hope this helps…