My guess is that back in the day of classical electronics-based computers, WIFI was somehow considered a hack due to providing a kind of magical connection that you can't easily see. Note that almost everything we use in subframe computers today is considered hackish the same way, even though they don't use WIFI at all because DRAY and FILT supersede it.
As for classical computers today, I guess it has to do with the fact that some of these computers end up being really small and thus you can have more than one in a single simulation, and they would of course break if they used WIFI unless they had all their WIFI particles reconfigured. I these computers might indeed be more difficult to build without WIFI.
I feel like that extends beyond computers too. Any save that relies on electronics can try to limit their use of elements, meaning things require clever workarounds and efficient use of space. Plus, this is The Powder Toy, and making things out of destructible elements when possible will usually make people happy ;)
It's probably because in real life, the first computer was huge and if you use wifi you don't get the full classic experience