Reason: nobody reads magazines anymore in the magazine format.
Well clearly enough people read magazines to keep all those hundreds of them in business. Just because you can't read news "articles" longer than a 140 character tweet doesn't mean "nobody" enjoys reading long-format articles written by people who actually know how to string sentences together and have an intent in writing that's more than just "get the fools to click the link". And by the way, the US book publishing industry is bigger than the big 4 sports combined -- by a huge margin. So you really shouldn't believe people don't want to pay to read.
My problem with Apple News+ is that for the $120/year, I find it cheaper to subscribe to magazines directly. Most of the magazines are at most $20/year, and although Apple's list is impressive and diverse, it's hard to find 6 I'd actually pay for. I also do actively pay for and read 3 magazines that are not on News+, and fwiw, I prefer the print magazines, so for Apple to get my interest, they'd have to charge a lot less than subscribing to the print copies of all the magazines I'm interested in.