Early on you probably don't need it for the load but for handling recovery if an application server goes down.
Prior to now if you wanted to run a passable production environment for a small application you'd probably do something like a single persistent store behind 2 application servers fronted by an nginx to balance load across the two.
Doing that requires nginx config and finding an off the shelf package for handling healthchecks and automated removal of failed items from the nginx load balance rotation. Now DO will do that for you at slightly above the cost of you rolling it yourself but with the benefit of being (probably) more reliable and requiring near-zero time investment.
Edit: Other threads have pointed out that keepalive on the VM works for recovery on single compute instances. Seems likely that this is for DO's larger client who need recovery and multiple computes with load balanced across said compute surface.