The truth about consumer buying patterns is most purchases are treated as lowest cost commodity, unless the buyer is aware or the price threshold is high enough[0]. When you don't have subliminal[1] and limited selection pressure (both of which exist in brick and mortar stores), coupled with a UI that makes it pretty easy to discover other brands, and coalesced signals (reviews placement etc), lowest price wins.
[0]: Put another way, if its expensive, it gets more scrutiny by the average consumer (whatever their definition for expensive is). The other circumstance is if they care about the category or are in the slice of shoppers who do quality research, which is less common than you might think, until the cost factor kicks in, usually.
[1]: This is brand awareness, and other related verticals. Effectively, this is what brand and mass marketing is about.