It ought to be illegal. Ideally I could choose to shop somewhere that didn’t do that, but like your boss said, they all do it. It makes shopping with small children hellish.
the UK is supposed to have made it illegal to have unhealthy stuff etc. near checkouts and illegal to include them in certain promos (e.g. buy-one-get-one-free) - I thought it had passed into law years ago, but when I had a quick look it isn't even due to take effected until 2025 and until then everyone is ignoring it anyway.
