Demand charges are now part of the default tariff plans for new residential connections in significant parts of Australia, notably SE Queensland and the major metro areas in NSW. It has nothing to do with solar PV, with one exception, that being if your meter needs to be upgraded due to installing a new grid-tied solar PV installation, then you transfer to the new default tariff structures. You can however opt out and move to a regular time of use tariffs (TOU).
In other regions where there are demand tariffs they are usually opt-in, with TOU being the default.
In my region the options are TOU (default) or Demand+TOU, where on the Demand+TOU tariff the difference between peak and off-peak consumption tariffs is much less.
People do hate demand tariffs here, partly as they are relatively new for residential, and partly because people are crap at maths and not even electricity retailer support staff can explain them.
It's not helped here by the way the tariff is presented.
e.g. instead of saying peak demand tariff is (say) $4.50/kW/month which makes sense (i.e. your peak demand for the month is X kW, so multiply that by the demand tariff), here it's expressed as 15c/kW/day (i.e. X kW x 15c/day x number of days in the month). The peak demand is only assessed during the peak demand window. It's little wonder people don't get it.
In the next year or so new types of tariff structures will begin being offered and become the default for new connections and meter changes, with solar soaker tariffs (off-peak middle of the day) and rewards for exporting energy during peak periods. I did a quick look at the average wholesale price for the whole year 2023 in NSW by 5-min intervals, and it's little wonder why:
We already are starting to get retailers offering free power for 2-3 hour periods in the middle of the day. I've just signed up for one. It's only 2-hours free each day on weekends, but heck in those four hours I can ramp the home battery charge rate to the max, put 150km of range into the car and maybe delay my water heater until then as well. Obviously I have to chew up my PV generation first but that's OK.
There are other plans with a free period everyday, but alas the balance of their tariffs don't work for us.