You do (still) need maps to hike the Appalachian Trail, but they’re probably not the kind that you expect.
There are two halves to every Appalachian Trail experience: backpacking the trail itself and navigating the communities that border the trail. While you don’t need to carry paper maps anymore to follow the trail (because it is so well-marked with blazes and signs), it’s very useful to carry information about the location of road intersections, town resupply options, shuttle drivers, and off-trail lodging. Most thru-hikers and section hikers leave the trail every few days to resupply, grab a meal, and clean-up, and having good intel about where to go and what to expect is important.
The best information resource to carry is David Miller’s annual AT Guide (available in print or PDF.) While it contains a detailed list of waypoints and descriptions of the trail as well as an elevation profile of its ups and downs, its greatest value is in the comprehensive off-trail reference information and town maps it provides about local businesses, transportation, prices, phone numbers, directions, and hours of operation. (See The AT Guide Review for details about the contents.)
I also recommend using Guthook’s AT Hiker App (iOS, Android), which is quite useful if you want to pinpoint your location along the trail with a Smartphone GPS (which can still operate when it’s not connected to cell phone service.) It’s better than carrying a trail map because it’s always up-to-date and the app lets you share information with other nearby hikers (like local Wifi passwords, the location of good campsites, water availability, and shelter conditions) using a virtual trail register capability. While you can carry a paper version of the AT Guide or tear out pages from it, I refer to a PDF version of it and Guthook’s App on my smartphone. Like it or not, a smartphone has become an essential on the Appalachian Trail. (See the Appalachian Trail Cell Phone Guide)
While I don’t carry paper maps anymore, it is still useful to carry a small compass so you can pick the right path out of a shelter area (which is not always obvious) and head in the correct direction when the shelter spur reaches the main trail. A compass is also more convenient to use than a phone for reacquiring the trail if you’ve stopped off to the side for a squat or pee, so you don’t end up wandering in a wilderness areas or (cough, suburban neighborhoods) trying to find the trail again. (See How to Find North with a Compass and Take a Pee without Getting Lost.)
While there are still some wilder sections of the Appalachian Trail, especially up in Maine, the trail signage and blazing up and down the trail is quite good, cell phone connectivity is nearly universal up and down the trail, and there are enough people around that you can always ask someone for directions if you’re uncertain where the trail is. The path is pretty beaten down too, so often you just need to follow the obvious groove in the ground.
Disclosure: The AT Guide and Guthook’s Guides have repeatedly given me free versions of their products over the course of many years. I use them because they are the best. If they weren’t, heck, I’d recommend something else.