In the UK we have a huge charity fundraising event called Red Nose Day and the public can donate online (or telephone if they want to speak to a volunteer).

The website probably sees 90% of their traffic on the day itself - millions of users - and the remaining 10% tailing off a few days later. Then nothing.

The elasticity of the cloud allows the charity to massively scale their compute power for ONE day, then reduce it for a few days, and drop back down to a skeleton infrastructure until the next event - in a few years time.

(FWIW I have no clue if Red Nose Day ever uses the cloud but it's a great example of a business case requiring temporary high capacity compute to minimise costs)

Everyone scales up around Christmas then scales down afterwards. What do THEY do with all the unneeded CPU-seconds for the rest of the year?

Plus bidding on spot-instances used to be far less gamed so if you had infrequent batch jobs (just an extreme version of low-duty-cycle loading), there was nothing cheaper and easier.

I've been out of that "game" for a bit, but Google Compute used to have the cheapest bulk-compute instance pricing if all you needed was a big burst of CPU.

It's all changed if you're running ML workloads though.