My cab has a -3dB point at 35Hz. An (utterly different) Ampeg 8x10 SVT is 40Hz or 50Hz for the high power version, so plenty of cab styles do go low(er).
I'm happy with 30Hz, not because it needs to be that low, but because it doesn't need to be any higher, at least with my kit (which has plenty of headroom).
I find my amps bass control is enough to tame boomy rooms.