QoS is not the technology used for hospitals, banks, airports, stock brokers and similar industries which need fast ping and guarantied network delivery. They use dedicated bandwidth, where QoS is used to alleviate issues resulting from congestion on shared networks.

Dedicated bandwidth is also what pays for new cables being placed between nations or continents. A new cable can often promise a small improvement in latency compared to the existing ones, which for a stock broker means a major advantage over competitors who use the old ones. The highest paying customers moves to the new one, which result in space being made available in the old cables, which tickles down to lower paying customers until its no longer worth selling dedicated bandwidth (which is normally in the from of separate wavelengths), which at that point it get used by multiple customers at the same time and people start to talk about QoS to artificially increase the number of possible customers on the same available bandwidth.

QoS is about selling bandwidth so it can pass over 100% usage. Dedicated bandwidth is about reliable network with fast latency. QoS is a way to increase the revenue of old cables and increase their lifetime. Dedicated bandwidth is what pays for new cables being placed in the ground or on the bottom of the sea.