Power Dissipation of Diode
But why in these diode datasheets, the maximum power is missing?

The maximum power dissipation is directly related to the maximum forward current and the forward conduction voltage (also pretty much related to forward current) so that is what is specified. Work with forward current and, if you need to know the power multiply the forward power by (say) 0.7 volts to 1 volt.
I don't recall ever seeing maximum power stated in a diode data sheet. It's always current that is specified. You get maximum power stated in BJT and MOSFET data sheets because current and voltage are not at all so easily relatable. You also get a safe operating area (SOA) graph in BJT and MOSFET data sheets but never in a diode data sheet from what I can recall.