Having printouts were necessary when: 1. you were using a DECwriter dot matrix printer as a terminal 2. using an ASR-33 teletype as a terminal 3. using punch

Having printouts were necessary when: 1. you were using a DECwriter dot matrix printer as a terminal 2. using an ASR-33 teletype as a terminal 3. using punch cards or paper tape 4. using a glass tty that could only display 24 lines 5. when you did not have a remote terminal, and wanted to spread your code out on a table and debug it