I keep seeing this ["I think that's why people get blasé about allergies and forget that they can kill"] being trotted out in various forms and I have no evidence for it.
Toobad, pretend restrictions make life more difficult for those with genuine restrictions. Pretend allergies are even worse.
People with Coeliac Disease being given unsuitable foods, because gluten-free has been confused with faddish eating.
Other parents complaining about having to keep lunch boxes completely nut-free, even though there's a child in the class who's severely allergic.
Hell, there's probably a thread somewhere about a vegan requesting the vegan option and getting salmon tartare.
But, in terms of actual fatalities, a restaurant owner in Yorkshire is currently being prosecuted for manslaughter by gross negligence, for failing to ensure that a customer with a declared nut allergy received peanut-free food. The customer died from severe anaphylactic shock. The peanut-laced-powder was allegedly used because it was cheaper than the usual ingredient. A 17-year-old girl also nearly died, the same month, from a peanut-tainted dish from the same chain of restaurants. Trading Standards investigated and found potentially lethal doses of peanut in a peanut-free meal.
This was not a one-off tragic case of switched labels or miscommunication -- but neither was it a deliberate attempt to harm. The restaurant chain would never, for example, have laced customers' food with rat poison. It was just totally cavalier to the fact that peanuts might as well be rat poison, for someone with a severe allergy.
The fact that managers, chefs and staff at several restaurants all participated in serving potentially fatal food to customers means that there is a real problem with uninformed, blase, careless attitudes towards genuine allergies, even in the food industry, and every attention-seeker who says 'I'm allergic to this' instead of 'I just don't like it' is contributing to this confusion. It's annoying to be served fish when you've requested the vegan/vegetarian option, but it's potentially fatal to be served peanuts when you've got a stated allergy -- people can and do die because someone who meant them no direct harm just didn't take it seriously.
(And, like OriginalMavis said, it's not even just about the ingredients -- worktops, utensils, cross-contamination has to be considered. No hope of that if the attitude 'a little won't hurt' persists.)