The traffic goes through this "new infrastructure" not out of necessity but because it's free and allows the user to pretend like a number of problems don't exist.
Terrestrial optical networks operate far, far below capacity to create artificial scarcity, which is to a certain extent necessary to recoup the capital expenditures in a competitive market, and is to a certain extent an abuse of an under-regulated natural monopoly.
If you could eliminate all adversarial factors and put every data service subscriber's payment for a single month into a pool, and that pool purchased only transceivers, passive optics and switches, and this hardware was distributed to every network operator perfectly fairly based on its contribution to the global maximization of available network capacity, then the delivered capacity to the end user could increase by something like 4.5 orders of magnitude with no substantial change in topology or subscriber or provider costs afterwards using the existing fiber, with a few more orders of magnitude possible with a fatter tree before the backbone costs explode.
With DWDM you can carry 100+ channels of 100Gbps over a single fiber today, with commodity, off the shelf components. Most fiber in the ground today is probably still lit with a single wave of 10G, if it's not just dark.
This distribution model is not even remotely a technical necessity, it's an arbitrary local minima reached largely by exploitative market distortions and adversarial economics.