I wonder the same, though the engineering under the hood is more interesting than I thought:<p><a href="http:&#x2F;&#x2F;perspectives.mvdirona.com&#x2F;2015&#x2F;12&#x2F;vpc-nat-gateways-transactional-uniqueness-at-scale&#x2F;" rel="nofollow">http:&#x2F;&#x2F;perspectives.mvdirona.com&#x2F;2015&#x2F;12&#x2F;vpc-nat-gateways-tr...</a><p>&gt; The connections are managed by a fault-tolerant co-operation of devices in the VPC network fabric. Each new connection is assigned a port in a robust and transactional way, while also being replicated across an extensible set of multiple devices. In other words: the NAT gateway is internally horizontally scalable and resilient.<p>Maybe it just wasn&#x27;t a priority.