NAT is an accidental consequence of IPv4 address shortage, but it turned out to a blessing in disguise. NAT gives every home a basic hardware firewall for free.
Everything, for better and worse (mostly worse) is connected to the internet nowadays. Your watch. Your dishwasher. Your TV. Your light switches. These devices are all comically insecure but because they can't accept outside connections because of NAT it's not such a big deal. IPv4 limitations make outbound connectivity easy but incoming connectivity hard. This is what you want 99% of the time.
NAT's firewall effect is purely coincidental. In fact, because people don't run firewalls because of NAT, attacks like NAT slipstreaming can open any port to any internal IP in your network by abusing SIP ALGs and fragmentation.
Wherever NAT is enabled now, a statefull firewall is a better solution. Thankfully, this is the default wherever IPv6 is rolled out to consumers.
Everything, for better and worse (mostly worse) is connected to the internet nowadays. Your watch. Your dishwasher. Your TV. Your light switches. These devices are all comically insecure but because they can't accept outside connections because of NAT it's not such a big deal. IPv4 limitations make outbound connectivity easy but incoming connectivity hard. This is what you want 99% of the time.