Why are mugs and cups effective marketing tools?

Why are from Visual.ly by enragedqueenmugs and cups effective marketing tools?:
A recent survey by the British Promotional Merchandise Association (BPMA) and Sourcing Planet has revealed that promotional items such as mugs are extremely effective tools for marketing and brand awareness. Low cost, usability and effectiveness of mugs make them an invaluable marketing tool, according to the BPMA.