I am a CFI-I and one of the airplanes that I instruct in is a WAAS capable C172 with the G1000. We do some LPV and LNAV/VNAV approaches at nearby airports. However, on some GPS approaches at our local airports the G1000 gives a glide sloped and indicates that we are shooting a LNAV/VNAV approach. However, if you look at the approach plate for these different approaches, there are no LNAV/VNAV or LPV minimums, only LNAV. Why does the G1000 have LNAV/VNAV approaches that don't exist according to the approach plate?