Why are vacuum flasks commonly used in urban areas?

Vacuum flasks are commonly used in urban areas because they are convenient for people on the go. They are portable and can keep drinks hot or cold for long periods of time, making them ideal for busy city dwellers who may not have access to a microwave or refrigerator throughout the day. Additionally, vacuum flasks are durable and can withstand the wear and tear of daily commuting and use in urban environments.

Vacuum flasks are not commonly used in urban areas.