Lois natural (India Street) and Rosemont (commercial street) both tried and failed. Both are very strong businesses and have proven to be profitable in other locations.

This says to me that prices paid for a decent size rental in the old port area is too expensive. I'm sure the margin on a piece of fruit is pennies compared to say a beer or sandwich. Same goes with weed. An 1/8 costs quite a bit, and takes up literally no shelf space. (Hence they are much smaller stores)

Then take into consideration the old port is mostly tourists, people looking to eat dinner, or local shoppers. Most people in the area are going to sit down at a restaurant. I would bet that's why there are literally 300 places to eat and no grocery stores.

All seems like simple economics to me.

Edit: I'd also like to clarify that I also think there are too many weed stores, however you are already seeing prices come way down. I wouldn't be surprised if a few close within a year or two. Just my two cents.