1) There are three "worlds" to Shadowrun: Physical, Magic, and Matrix. Almost any task can be accomplished in any of the three worlds. Need to get by a camera unseen? You can sneak past (physical), benefit from an improved invisibility spell (magic), or the hacker can edit the team out of the data feed (matrix). Naturally, certain things are most easily accomplished in one world, and those things that are most easily accomplished via the matrix will be best done by a decker/technomancer.
2) Technomancers' Living Personae can run in AR and Hot Sim VR. They cannot use the Cold Sim VR matrix user mode.
3) AR hacking is a thing. (personally, I play a decker and generally I prefer AR whenever feasible... no biofeedback damage, you can still dodge incoming gunfire, etc )
4) Technomancers are to Deckers as Adepts are to Sammies. (speaking personally, one of the reasons I don't like TMs is they can do everything a decker can do, without needing to spend resources, PLUS they get "matrix spells" and "matrix spirits" that deckers can't have. They're better than deckers in about every way, yet conventional wisdom seems to be that TMs are somehow worse in every way. I totally don't understand how anyone thinks that, but lots do.)