A great power that people do not even realize they have lost is the ability to do things on one's own system without a network connection. This may sound obvious and stupid to some, although there is an entire generation being raised to view The Cloud™ as the primary way to get anything done whilst seated in front of a screen.
But even for those of us who have been around since before the normalization of Services as a Software Substitute, how many still use Google search as a form of spell check, or a calculator? Copying special characters into clipboard? Dictionary, thesaurus? A combination of convenience and laziness is what has manifested this situation. And this is dangerous not only because these things can be surprisingly revealing but also because it can lead to eventual dependence upon Google or whichever FAANG is supplying the disservice in question.
It might also surprise some just how much can actually be done predominantly locally just on one's own box. Speaking for myself, it had taken me way too long to discover that email clients weren't just a relic found in the boomer stratum, but an actual useful way to interact with email without the expectation of a constant network connection. Beyond caching scenarios, there is huge swath of commonly-online applications which can be taken totally offline including but not limited to; mapping and routing, language translation, weather monitoring, virtual assistants and more *some assembly required.
But regrettably, we are quickly entering into a world in which people will be increasingly shocked to discover that one can do such basic things without internet as editing documents or listening to music. And so whenver I make recommendations for any techical solution, I will try to always supply either an entirely offline or at least locally cacheable means of accomplishing it.