According to this, Floating IPs can
be instantly remapped, via the DigitalOcean Control Panel or API, to one of your other Droplets in the same datacenter
What prevents Floating IPs from pointing to Droplets in different data centers?
Because of the inherent workings of Internet routing and the sizes of the blocks allocated to network service providers.
IPs are allocated in blocks, not individually. This means it's not as trivial as it seems to route a single IP to a different datacenter.
If you are just want load balancer for http/https traffic take a loot at our SaaS Load Balancer https://failovery.com
Why wouldn't I use either something like haproxy or DO's own load-balancer services?
It is possible to have a floating IP between datacenters. Amazon Elastic IP's do it within the same region. IBM cloud (formerly softlayer) has the best implementation I have found since there is no regional limitation and no NAT involved. They call it global IP.
Actually it does. IBM cloud shows that it is possible. There are some here suggesting that DO does not do it because it is not possible. It is not done because it is not easy. If it were, IBM cloud would not be one of if not the only service that does it.
If DO were to do it they would certainly get my business. Floating IP is not useful to me without datacenter redundancy.
floating IPs and dynamic load-balancers are far more useful, imo, than pure floating IPs :)
Also want to add that there is another company that does it in addition to IBM cloud. Their service looks even better in some ways because it includes the monitoring and automatic failover features.