Btw during last night I gained about 60 trophies and a few gems just by defending well against some attackers - 59 trophies gained by 4 raids on my base (one of them got 100%, others about 20-50%), that’s a motivation for setting up an effective base, I’d say!
One more argument for not increasing/easing trophy gain by attacking is that, especially by free food videos, some players might just perform hundreds of raids per day… if every attack (unless failing completely like 20%) almost grantedly gives you +trophies, then nobody could compete at all without free food videos or spending hundreds of gems just for silo refills each day. Also, not everyone has enough time to be online for several hours each day to perform a lot of attacks.
With a more offensive-favoring trophy gain distribution, clever base building wouldn’t be rewarding at all. The way it is balanced currently, clever base building gets rewarded. And after all, everyone has 1 base and can do his best to make sure he has an effective layout (good layout but weaker towers can be a lot more effective than bad layout with stronger towers!) at least, so everyone can get his defenses right, no matter how many food is available to him.
That makes sure skill (picking the right opponents for one’s own attacks, getting gate down on raids, setting up clever defense) is rewarded, too, and not just pure quantity (number of attacks performed) of one’s actions.
And I say this after epic-failing two attacks today, each giving me about -40 trophies, quite effectively cancelling out all trophy gains of my other raids lol… so it can feel quite harsh sometimes, but again, if I can use my defense to hold/increase my rank, I don’t mind a relatively restrictive trophy gaining system for attacking. Also, I could just use some gems to resurrect if I just wanted not to lose a particular raid, but I can’t just buy a better defense for one attack on my base, and I also could have decided not to attack exactly that hard-looking base but just go for an easier one.