The problem with Single Pair Ethernet is: nothing supports it.
You don't see off the shelf home routers that just so happen to have SPE support in every LAN plug, or USB Ethernet adapters that support SPE alongside the normal 10/100/1000Base-T, or SoCs that integrate an entire SPE PHY. So it ends up stuck in this adoption limbo.
The advantage of normal Ethernet is that everyone already has the hardware for it, and SPE doesn't have that advantage.
You don't see off the shelf home routers that just so happen to have SPE support in every LAN plug, or USB Ethernet adapters that support SPE alongside the normal 10/100/1000Base-T, or SoCs that integrate an entire SPE PHY. So it ends up stuck in this adoption limbo.
The advantage of normal Ethernet is that everyone already has the hardware for it, and SPE doesn't have that advantage.