The grocery industry is definitely a developed industry; these folks have not been letting the grass grow under their feet for a long time now. And yet the supermarket is, in the long, long history of food retailing, quite new. Figure that food retailing is over 3,000 years old, and the supermarket is more than a score short of a century - thus the supermarket has only been present for the last ~2% of the food retailing industry timeline.
And self-service, and packaging, is only a very few years older. The self-service innovation is generally credited to Piggly Wiggly in Memphis in 1916; less than 100 years ago.
Credit for being the first supermarket is generally given to King Kullen in Queen's New York in 1930 - less than 80 years ago.
Since those first key developments the industry has not been allowed, since there are always new competitive challenges to deal with, to slide into complacency. The industry has had to remain in a developed state, rather than keep the old ways of last year and the year before that.
From the 1930's through the 1980's the intra-industry competition kept the industry on it toes, and becoming ever more efficient.
Then, as non-grocery discounters (Wal-Mart, Target, ...) and warehouse stores (Costco, Sam's Club, ...), added groceries and made themselves into supermarket-competitors, the struggle to survive and reinvent themselves became even more intense for supermarkets.
This is an industry that must keep itself on the developing edge or they'll be out-competed, out-moded, and out-dated.
Oops
"By the 1950s, the transition to supermarkets was largely complete, and the migration to suburban locations was beginning. Some chains were more aggressive with this move than others. A&P, for example, was very hesitant to expend the necessary capital and move outward, retaining urban locations for perhaps longer than was prudent. While the company tried to catch up in the 1960s, its momentum had vanished, and the once dominant chain eventually became something of an “also-ran.”"
"A&P, as was its custom at the time, arrived somewhat late and unprepared for this party. It attempt at discounting, WEO (Warehouse Economy Outlet) was something of a disaster, plagued by distribution issues and by the fact that its numerous smaller and older stores were not capable of producing the volume required to make discounting work (but were converted anyway). This was one of several factors that preceded A&P’s major meltdown of the mid-1970s."
A Quick History of the Supermarket : Groceteria.com | Supermarket History + other sources