It's a prisoners dilemma. The total market share remains the same, but if only one grocery store was on DD they'd be at an advantage over those who don't

These grocery stores are all going to continually lose market share to Amazon, Walmart, etc. as online ordering increases. The pricing of in person grocery stores is outrageous and the experience shopping at them is annoying. I hope to see many go out of business sooner than later so we can have better businesses take their place!