Scalability is also an ongoing process where one has to meet unforeseen demands. Often times critics are quick to dismiss ideas with the thought that "such and such can't possibly scale," but some of the most popular products and services we use are still currently failing to scale (e.g the internet in general, services like netflix, ect).
However, these products and services fail to scale "gracefully" over the period of ten or so years so the technologically eventually catches up only up until the point where market demands increase all over again (e.g. email started as simple text, then people wanted to add images as attachments, eventually people wanted to stream movies on the internet, and now we're dealing with 4k videos).
It's a constant balancing act where major products are always "failing to scale," but they fail in such a way that consumers end up with better and better products each year.
An interesting talk on the topic: