Hot Water System

To my understanding, a conventional boiler heats up all the water in the tank, even if it’s not being used/needed. You can schedule when the boiler comes on with your central heating program box.

A combi boiler only heats up water when it is needed. Therefore saving you money. A disadvantage of this is that you need to run the hot tap for a bit, before the boiler has chance to kick-in and heat the water up.

Question:

If a combi-boiler comes to life by the taps being used, what is the point in scheduling the hot water on the central heating system?

Thanks in advance