What size geyser? And how many people taking showers?
The more people the hotter the temp needs to be to meet everyone's needs. Hence the mixing of hot and cold water.
If one person, then you could argue for a lower setting and only draw water out of the geyser. But if there are more uses for hot water, then more hot water is required at a hotter temperature.
150 litre kwikot, 2 people in the house.