What is the most annoying activity on data-driven approach in marketing?

My top 2 reasons why companies DON'T do this: 1. Lack of marketing data talent - Marketing requires a really broad array of skills. Marketing team might be better equipped at execution, storytelling/creative, community building, design and not data. Lack of marketing analysts or data driven talent on marketing team can be a reason for this. 2. Infrastructure- measuring marketing takes some work and investment to set-up. Otherwise you have no data (or worse, bad data) to analyze.

You need to get the basics right for data driven marketing to work. This means, you have product market fit, idea about channel working etc. Without these, setting up data etc is not worth it for early stage guys. The big ones anyway have the budget, know how etc to go about it. They also got the scale to invest and generate ROI out of the data.