Actually, it's a neighbourhood and the St. Lawrence Market is a market. The impression that it is a tourist attraction is just incidental.
Agreed. Most of the south market is butchers, fish mongers, cheese shops and vegetable stalls. I don't know about you, but when I'm a tourist staying in a hotel the last thing I'm likely to buy is a rack of lamb, a few pounds of talapia and a head of broccoli. Those things don't survive the trip home in a suitcase very well.
Saturday's are by far the busiest day at the market, and there are many tourists, but if you look carefully it is mainly the locals doing the shopping and the tourists doing the gawking. During the week the market is very quiet, but those who are there are there to buy, either groceries or lunch, so the percentage of visitors who actually spend money is likely far higher than on Saturdays.
As for the neighbourhood, aside from those perpetually taking photos of the Flatiron, there's not much that is purely for tourists. It's a nice neighbourhood to live in, it has many attractive restored historic buildings, and it's a model of a walkable mixed-use/mixed-income community. That's why it's on the tourist circuit -- not vice versa.
They can still have the day off. They just need to hire some additional employees.
Again, much of what makes the market attractive is that the stalls are mainly family run by people who are knowledgeable about their product and eager to foster long-term customer relationships. Stick a bunch of part-time staffers in those stalls and the experience would diminish. It would also be expensive and I could easily see some of the more niche stores go under to be replaced by blander touristy crap. Right now the maple syrup and silly t-shirt vendors are in the minority and I hope it stays that way.
If anyone wants an example of the SLM should
not become, visit the Chelsea Market in Manhattan. Sure it is a beautiful space and home to the Food Network and dozens of specialty shops; however, it is 100% tourist attraction. I can't really envision any local going to that place weekly to buy groceries. Even as a tourist I wouldn't go back, because there's nothing more to see: it is just a building, not an experience. But yup, it's open 7 days a week.