Because all of the XVIII century newspaper editors were spiritual being who disregarded money. Is that your point?
Also, I fail to see how a line saying "This news is republished from such other newspaper", or paying a fee to the original writer would have hindered the spread of the news (less important news could have been omitted, but not the headlines).
Yes, they had another set of ethics so in their eyes it was not bad. But to say that, without those ethics the news would have not spread that far is a big overstatement. Nowadays, all newspapers "copy" news from the press agencies by paying and giving proper citations and it seems that it works.
It is like saying that, because these newspapers printing blatantly one-sided and partisan reports about the facts helped the American Revolution, all newspapers today should never try to be impartial or objective.