Newspapers are more advertising driven nowadays. Though it always was important for income, the newstand and delivery sales paid a lot more of the costs than they did today.
Also, newspapers were bigger – physically, each page was larger. So even if you got as much ad space as you do today, there was more room for news and features.
I don’t have any handy, but when I was looking at NY Times in the 30s, there were far fewer ads (partly due to the Depression) and much more space – each sheet of paper was bigger. I think they were able to fit in eight columns per page instead of six today. Tabloids also were a little bigger. Of course, the Times didn’t have comics, but they put news in their place. Also many papers of that vintage (e.g., The Daily News or The New York Sun) didn’t have comic pages per se – they scattered the comics throughout the newspaper.
Most comic artists have complained about the trend, but one advantage is that each newspaper can put more comics in each comics page, which is a good thing for them.