Traditionally these have either been somewhat impractical (e.g., the Selectron tube) or are considered to be suitable only as read-only memory (e.g., EPROM, EEPROM/Flash memory) since writing data takes significantly longer than reading.
Traditionally, these devices have been either difficult to use (like the Selectron tube) or only useful for storing information without being able to change it quickly (like EPROM, EEPROM/Flash memory).