Why doesn't a passive x1000 oscilloscope probe have 1000M Ohm impedance?
They all use 50 Ohm cable for optimal BW of >50MHz thus Rin is 50MOhm to 400M with (?) 2 stage dividers. Using 1Gohm requires active FET probes rated only for 25V or so.

It would also become unsafe at hiV with creapage going to insulator resistances of 1GOhm. Leakage would cause Partial Discharges. (faults)

Why would you want 1GOhm for high voltage in a tiny probe?


  Use C ratio divider for HVAC. Then use a divider with 50 Ohm termination.


2000:1 probes use 93 Ohm coax to reduce capacitance.