TLDR: if you want less cups you put up a weak defense, if you want more cups you put up a strong defense.
The one defense hero are people are either maintaining cups (hardly anyone will attack as a less than 5 hero win is effectively a loss when it comes to filling the raid chest) or don’t understand the game mechanics.
The weak defense (5 heroes) is used to drop cups and there’s more food to be gained from raiding at some cup values than others: in my experience 2400-2600 or so is exceptionally bad for example. Also if you are further down the ladder than you “should” be, you can fill raid chests more quickly to try to push special chest generation.
Finally the vicious defenses you mentioned: if you either care about having the highest cups, or if you’re on a cup push (sometimes I like to see how far I can get, accidentally tried the other day and slipped into the top 100 before I ran into a strong defense and an absolutely awful board, ah well haha) then you put up a strong defense.