I wasn't around in r1, but was in r3...cargoships were still there, but used more as yet-another-frigate-class-ship-flak rather than resource stealing outright.
I certainly don't remember anyone complaining about them, either.
With as much resource hoarding as we have had the last few rounds, a cargoship that stole saved resources wouldn't be any more of a nuisance than SK's are--and would possibly open up some new and interesting tactics.
Not to mention having yet-another-(class)-flak ship