There's nothing wrong with leasing transport. Almost all of NTT's network is leased, and pretty much everyone agrees they're a top flight network.
The thing that makes HE unique is that they only sell full ports. They don't do fractional billing or 95/5. You pay for 10gigs on that 10gig circuit, regardless of use. This leads to networks running HE ports near max load at peak time. From HE perspective, this is great because it's super easy to plan for and scale out. You're never surprised by a customer who goes from 3 gigs to 92 gigs on that 100gig circuit.
Never said there's anything wrong with it, it just changes the capital expenditure and worth from physical to virtual (peering agreements). Companies like Century Link, AT&T, Verizon are in a slightly different category with abundant in ground infrastructure (that has extreme tax benefits in the US).
If you look at CAIDA ASRANK, very few of the top-20 ranked ASes in the world, as ranked by diversity of peering, number of BGP adjacencies, etc also own/fully control the dark fiber their inter-city router-to-router links are operating on. They leave that to specialists like Zayo.
Telia has POPs all up and down the US west coast but it's certainly not their fiber connecting them together.
The thing that makes HE unique is that they only sell full ports. They don't do fractional billing or 95/5. You pay for 10gigs on that 10gig circuit, regardless of use. This leads to networks running HE ports near max load at peak time. From HE perspective, this is great because it's super easy to plan for and scale out. You're never surprised by a customer who goes from 3 gigs to 92 gigs on that 100gig circuit.