AWS encourages you to use VPCs for service-internal addressing. Yes, you can rent "elastic IPs", but in the AWS mindset they are special and to be used only for NATing Internet endpoints to your services. It's based on end-to-end addressing being special and a scarce resource. This is compatible with the traditional corporate intranet style of thinking, but it's also in the opposite of internet end-to-end addressing and they are in no hurry to change it.
ipv6 has a provision for locally routable addresses, because yes publicly routable addresses should be special. They should just also be free.
Link-local addresses are not routable and are not meant for application use, they're just for low level things like neighbour discovery and router advertisements (analogous to IPv4 ARP/DHCP).
There's also ULA that can be used for non-internet connected networks and some other special scenarios, but it would be a bad idea (and against recommended practice) to use them to port your RFC1918 addressing to IPv6.
"End-to-end addressing" is typically an end user issue, where end users use NAT. In the early days of the internet, nobody used NAT.