one thing to understand would be what incentives are in place. e.g., how is the "free" lunch paid for? does your employer directly employ cooks & pay for the cost of ingredients? Or is the catering outsourced? if it is outsourced, what incentives (if any) does the catering provider have to cook food that will be eaten by staff? it might be the case that catering is provided on some kind of fixed-price basis over a time period, so in the short run there may be incentives to spend as little as possible on ingredients, +/- how this might impact the chances of the arrangement being extended or terminated.
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presumably your employer may offer free lunches as one perk to attract talent, but also to encourage employees not to leave the office and keep talking shop or building relationships with each other, or just having a quick lunch and getting back to the grind, all of which could have value to the business. so it would make sense if the business could align incentives so that the food is just tolerably good enough that most employees want to eat it sufficiently often, but that the cost of providing it (including over-catering and corresponding loss to waste) is low.