Because the content of the questionnaire is the data you need for your thesis. Writing a thesis should have its own arguments, which need the support of materials and data. You can only summarize other people's data, not your own scientific research results. To complete your own scientific research, you need to design your own questionnaire and collect the data for yourself before you can complete your thesis. Because the content of the questionnaire is the data you need for your thesis. Writing a thesis should have its own arguments, which need the support of materials and data. You can only summarize other people's data, not your own scientific research results. To complete your own scientific research, you need to design your own questionnaire and collect the data for yourself before you can complete your thesis.