Answer:
Different aspects to be considered:
First of all, the steakhouse probably has the most clients between 6 to 8 PM, that is why discounts are not offered during that time.
Second, the discount is offered to only a certain group, employees of other stores, because it is a promotional strategy aimed at increasing the number of clients during slow hours. Since this is a fancy place, it is probably expensive also. Most employees would not actually eat there except on a special event, e.g. birthday or anniversary dinner. Even with the 20% discount, not many of them will actually eat there.
This is something nice to offer, since a shopping mall is a close environment where a lot of different people work together, even if very few will actually take the offer. It is normal that different stores have distinct promotions for the employees that work there. It is similar to offering perks that help create a better working environment between the employees of different stores.
