Why is a telephone directory not a good source to develop a sampling frame?

A telephone directory is not a good source for developing a sampling frame because it may be outdated and not reflect the current population, as people frequently change phone numbers or move. Additionally, it often excludes individuals without landlines or those who use mobile phones exclusively, leading to a biased sample. Furthermore, the directory may not include unlisted numbers or individuals who prefer privacy, further limiting its effectiveness as a comprehensive sampling frame.