Many of us in the east cannot, as a practical matter, spend any meaningful time in our gardens from late June until first frost due to mosquitoes. This year, they have been especially bad due to an overabundance of rain. The rain situation has also led to enhanced weed growth. So there are all these weeds and we really can't get at them until November. Further, organic mulches breakdown faster and weeds grow more quickly in our hot, humid summers. It's a real problem. So, I can see where landscape fabric might be a bad idea in the PNW or California, but in the east, where conditions can be very wet/tropical for half the year, you'll take any help you can get with the weeds.
I had landscapers use fabric when my backyard was given a makeover in 2010. Today, much of it has been compromised by tree roots from below and weed roots from above. Nature reclaims most of our efforts, given time.