Short answer: Because the base may not be 10.

Long answer: Because if you put a number, people expect it to be accurate. If it was 6x faster, and you said 10x, people may call you out on it.

It's meant to signify a step change. Order of magnitude change = no amount of incremental changes would make up for it.

In common conversation, the multiplier can vary from 2x - 10x. In context of some algorithms, order of magnitudes can be over the delta rather than absolutes. eg: an algorithms sees 1.1x improvement over the previous 10 years. A change that shows a 1.1x improvement by itself, overshadows an an order-of-magnitude more effort.

For salaries, I've used order-of-magnitude to mean 2x. Good way to show a step change in a person's perceived value in the market.

I think of "an order of magnitude" as a log scale. It means somewhere between 3.16X and 31.6X.

"10x" has been cheapened / heard enough / de facto, is a more general statement than a literal interpretation would indicate. (i.e. 10x engineer. Don't hear that much around these parts these days)

Order of magnitude faces less of that baggage, until it does :)

- sounds cooler

- 10x is a meme

- what if it's 12x better

10x is too precise.

Because it's not 10x?

Because "magnitude" has cool gravitas, something in how it's pronounced. And it's not meant to be precise, it just means "a whole lot more".

5x faster is an order of magnitude bc of rounding