Well, I have an answer to this, there are various stages at which, the king must be there to mark a siege or raid. That time your loot increases.
It goes the same for general raids but only thing we don’t notice it because the king is always going towards the gate. In a straight open base, at about 40% of the ‘PATH’ a siege is given, at the end of the path tiles, just before the gate area, ‘RAID’ is given. Victory after bringing the castle down.
In case of a few towers, maybe 60% of ‘PATH’ crossed - Siege. Destroying Towers - Raid.
And as a matter of fact, waves do not contribute in the Victory Percentage. It doesn’t matter you have full maxed waves or no unit. Even If you don’t destroy a wave, still 100% is achieved. What matters is location of king, Traps & Towers. If your king takes heavy damage from castle arrows, simply hit the castle once & stand away from its reach & let the units do the job.