I am neutral on this issue in so far as I have produced both "real" decks or better to refer to them as "physical" decks, and I've produced apps, so I am not pushing any particular agenda.
Nevertheless to simply compare apps to the "real" thing and then dismiss them as lacking is a somewhat simplified conclusion. I think you have to define what you expect from an app, or what you assume that an app is capable of doing. Of course they may not have the touchy feely intimacy of a physical deck, just as e-books/apps don't have the smell and feel of a nice leather bound book. But part of the evaluation must address content, the story, the information, and how its presented. An e-book of Jane Austin, or your favourite poet may seem technically cold and somehow inappropriate, but how about if that e-book not only allowed you to read the poetry, but also offered the option of that poetry being read to you by its author? How about that e-book or app that offered the ability through addition text, audio, video to better explain, teach and generally convey the information, from a technical reference book to..... tarot cards. How about if the e-book or app had the ability to zoom in and show the images at sizes and detail even greater than the real deck. Surely such capacity would be useful for study or meditation, and are criterea that should be also be considered. Or that the readings spreads YOU can generate "through" them (not random creations "BY" them) can be captured visually, saved for future reference and comparison, and be e-mailed to a client or friend. In my opinion that adds up to a lot more than just a novelty to fiddle around with for passing away the time on the subway.
I designed my apps to offer all those features. I didn't however design them to produce cheesy generalized canned readings. That kind of thing, I do find quite silly. But when viewed as a "tool" in the hands of a human reader. I consider apps a worthy alternative either for back up, convenience and in some circumstances publicly more discrete.
With all that said, not all apps are made equal, what each is capable of varies considerably. But overall they shouldn't be dismissed to quickly in their entirety.