Merits are money...it may not be obvious if it is your first cycle, but at the end of the 3rd cycle, it's easy to get 5 millions.
Now of course, you get merits for taking down enemy ships only in the rights systems...
OP has not mentioned PowerPlay. Did you mean you killed enemies who attacked you in a non civilized system or Anarchy one? All ships in these are Clean and there's no bounty as there's no law there to go by.
I have pledged to a power and when I enter my HQ system I get interdicted by the "Ememy" and shoot them down and get nothing in return for blowing them up. Nothing!
Loads of credits m8 , for me atm 500.000 credits a week and 50% more bounty claim each criminal kill , next week and a half a special pew pew device and im just a lousy rank3 , damn kids wont let me play much(Arissa is nice if you are a bounty hunter type)
not being paid direct is not paid at all lol(should tell my boss)
And I think it's also strange that none of them has a bounty on their head. Either there should be a pay by bounties or at least one merit per kill. Or more realisticly both for those guys are killing our traders - and telling me all the time they don't like me to be in my own system ; )