Many years ago before National Geographic came to the party, there was a software company in San Francisco called Wildflower Productions, and they marketed a product called TOPO! (that should not be confused by similar names on similar products). This software product interfaced with several different map database products. For example, there was one map (on CD-R) for each of the major national parks in the USA. I had those, and I had the entire California set of maps from coarse scale down to 1:24000 fine scale, and this took up a dozen CD-R disks. This took place about the same time (ten years ago?) that Wildflower sold out to National Geographic, so suddenly the NG logo or copyright appeared on everything. Within my computer and within the set of CD-R maps beside it, I had 99% of everyplace where I operate. If I traveled much more to other states, then this would not be practical.
When the map database is somewhere else like on a web site, there are advantages and disadvantages. That allows the vendor to update the maps, if they have a mind to do that. Unfortunately, most of the maps come originally from USGS, so the vendor probably doesn't want to fool around with updating the topo data. Some subscribers don't mind paying bucks per year to have access to these. Some don't even mind the online connection times to download the maps. I believe that most of the online topo maps are available for free.
Fundamentally, electronic topo maps available to your desktop computer are great tools, especially if you have a wide-format color printer. If you try to access fine scale topo maps purely from a small-screen portable device, it will become an exercise in futility.