You're making a lot of assumptions that aren't terribly valid for most use cases. Not to say that strict consistency requirements don't exist, they certainly do, but they are the exception rather than the norm. A one person startup doesn't usually care too much about losing a bit of client data.
> If you have a full-time ops staff, throwing another marginal piece of infrastructure on the pile isn't much of an issue.
That's a rather insulting description of Redis, care to elaborate?
It's nothing like insulting. Think of it like absolute and marginal costs. You have absolute infrastructure -- the sum total of all your infrastructure -- and you have marginal infrastructure -- bits and pieces that can be added and removed. If you have no Redis and then you have Redis, NewAbsoluteInfrastructure = OldAbsoluteInfrastructure + Redis, and Redis is your marginal infrastructure.
> If you have a full-time ops staff, throwing another marginal piece of infrastructure on the pile isn't much of an issue.
That's a rather insulting description of Redis, care to elaborate?