AdinTheDark I guess, I mean what's the alternative?
Someone fails an attack. They can start building troops to mount a defense for a potential pre-re, total potential losses 0 to 2X. Or they can stagnate and let their allies hit them 2X and also get retalled, total potential losses 2X to 3X.
I guess the defender could try having an ally hit for the first, wait until that prot ends, then hit again and also retal. But that's banking on the enemy having available armies and coordination for such a tactic.
The best thing to do imo would be to not oversend on the initial attack, that way if it fails the remaining garrison can stand a chance to defend against whatever happens.