In some ways, retail mitigates risk. Kind of like a little cash safety net.
Retailers buy in advance. If I forecast a million units sold through in my fiscal, my job is to get retailers to buy like 1.4mm units in advance of launch to stuff the channel. That's a big chunk of cash for me in my current fiscal. Even if the game sells thru half of that, under forecast, I don't really have to worry as much about that right now - I got all the cash upfront.
Via digital, if I forecast 1mm units and the game sells half that or totally tanks.... Despite higher margins per unit, I'm SOL this fiscal as I won't see any big cash influx. Better hope big sales and discounts get you the revenue longer term.
It's also a very different audience buyer.
Mom isn't going to PSN to buy their kids Christmas presents. You want a well trained GameStop employee to inform her what your biggest games are this holiday for gifts. To do that, you gotta play ball with the retailers. The browsing experience on digital stores is shit compared to a shopping experience for the majority of gift buyers and broader consumers. People hit digital marketplaces when they know what they want. Log in, buy, play. Very little browsing. Lower catalogue sales too unless you're one of the few games to "trend."
So, lots of reasons retail is still important despite digital being what most would want. It's just a slow evolution but clearly happening as younger generations grow up with this shopping behavior and digital stores update to accommodate more casual shoppers.