First, most ACH transactions clear in the same day [0]. Second, that's also completely ignoring newer networks like clearXchange / Zelle, which clears in minutes [1].
"Specifically, the NACHA Operating Rules require that ACH credits settle in one to two business days and ACH debits settle on the next business day. Recent enhancements to the NACHA Operating Rules now enable same-day settlement of virtually all ACH transactions."
Transferring money with ACH takes multiple business days, this is not at the forefront of digital technology.