On the basis of qualitative studies which make it possible to understand the deep and updated motivations, the quantitative studies make it possible to give a quantified point to the insights / information / levers thus revealed by the qualitative studies.
Without a qualitative study beforehand, quantitative studies only measure internal a priori and therefore validate your own beliefs without making the effort to fundamentally take an interest in the market and want to conquer it.
The reasons vary depending on your needs. If you are launching a new project, product or service, this can allow you to:
Test the concept from the start: The first advantage is that you will be able to consult your market, to see whether or not it is receptive to your project. And this before you even design anything, since you only need your ideas to create the questionnaire.
Validate your targeting: You can directly question your target market, and identify your best prospects. Are your assumptions about your ideal customers correct? Is there a more interested segment? Ask the right questions, and identify the most interested profiles.
Test a need, identify expectations: Is the problem you want to solve real? What frustrations does this generate in your prospects? What are their specific needs?
Understanding the habits: In what context do they need your offer? What solutions or alternatives are they using today? What are the advantages and disadvantages of these solutions …
Get feedback: You will be able to present your product to hundreds of people, and let them speak, so they can tell you what they think. What they like, what they don’t like, what they would like …
More generally, the quantitative study makes it possible to take a step back, to limit the impact of bad intuitions. You get an objective and representative vision of your market. While validating key points of your project.