The point of getting trophies for failed attacks is it rewards the active player that is attacking instead of 'rewarding' the inactive player.
If players are attacked then they still lose trophies if they are beaten so it will eventually level them off at the # of trophies they can pretty much hold onto via re battling. What the suggestion does is prevent players artificially lowering their own trophy count by fake attacking other villages. What it doesn't do is prevent other players being artificially boosted by getting trophies for winning when all the opponent did is zap them or drop one goblin down but it would still be an improvement as it at least addresses half the issue from those battles.
