Why do people say 10k instead of 10000?

People often say "10k" instead of "10,000" for brevity and convenience, especially in casual conversation or written communication. The "k" stands for "kilo," a prefix meaning one thousand, which makes it quicker to express large numbers. This shorthand is commonly used in contexts like running races, financial discussions, and social media, where space and time are limited. Additionally, "10k" can feel more relatable and less formal.