PS: Older showers used up to 4 gallons per minute, high flow showers can get well above that. Worse and old style washing machine will often use 40 to 45 gallons per load.
Landlords have no incentives to install toilets and appliances that use less water (or electricity), and every incentive to go cheap (which will also be less frugal). They don't incur any of the running costs. And since it is private property they can't be forced into doing anything. Tenants rarely have rights to install more efficient ones either.
Having individualized water meters isn't nearly as efficient or convenient for large apartment complexes as just doing it centrally, especially when the landlord is also using a large chunk of the water (eg for communal lawns). Rent control regimes prohibit separate fees (or higher rents) including the price of the water, so landlords in rent control situations will pass such costs directly to residents any way they can, even if it is inefficient. They'll also pass the costs of upgrading fixtures like toilets and showers, since they're not allowed to charge for them either.
In one house it would have cost $20 more to replace a toilet with an efficient one, versus repairing the existing leaking old one. I wanted to pay that $20 extra - they refused leaving me paying higher water for several years.
In other words, it was intended to be a restriction on truly frivolous use, while still allowing all the basic day-to-day without worry.
Swimming pools actually use less water per square foot than an irrigated lawn. About half, in fact. So lawns might be one answer to your question.
Don't worry, I'm not using Californian water. ;)