There is a fundamental misunderstanding (intentional or not) with these types of studies and claims. Limited-time promotions, e.g. a 10% off sale, work on short timescales that are easily measured. You can easily say what the ROI is of an advertised promotion, and it is often positive. (Side note, these promotions have a more-difficult-to-measure detrimental effect on your long-term profitability, closely related to…
Would you say that might be a source of bias?
Look at SpaceX and Tesla. They barely advertise and have huge brand recognition.
I'd buy Sennheiser over Beats. Krispy Kreme over Dunkin. Costco.
My partner loves Zara.
I don't have a high opinion of brands that advertise.