Yeah this sounds bad. If the company stops giving “free” pizza bc/ someone takes not 1/8 of a pizza but 1 pizza, then you know how much they value, or rather do not value your time.
Hard to see how a manager could be this inept.
Same mentality is why we can't leave a basket of unattended candy outside the house on Halloween, for Trick-Or-Treaters to share: Inevitably someone will just take the whole basket. It's not about the cost of the candy, it's about not enabling jerks.
When in your local park there are no benches to sit because half of them were dismantled and sold for scrap (true story) you can think how government spends too little on park maintenance or policing, or you can think how people are being selfish jerks to each other.