I think it's purely a liability thing. If an employee messes up and someone allergic tries to sue, the warning is always there. I don't think it's anything to worry about, it's to make sure there are no loose ends. My best guess.
Exactly. In a society of litigious nincompoops, companies do need to protect themselves. And, of course, there are those people who may have life-threatening reactions from one airborne trace particle that could have landed on a product being made elsewhere in the facility, so those people NEED to know if there's even a one in a million chance of anything that could put them at risk.
Also, one thing to note for a LOT of companies is that it can cost hundreds of thousands or MILLIONS of dollars to set up a dedicated vegan facility if you're in the business of producing vast quantities of both vegan and non-vegan products. We've spoken with so many companies over the years who have said they'd LOVE to be able to set up a dedicated vegan wing in their production facilities, but with how small the vegan market is, they'd never, ever be able to pay for building such production areas just to suit the vegans who are extremely fussy over allergen notices (as these days, few seem to be overly concerned about it). Of course, money talks, and if they are going to risk bankruptcy to cater to a fraction of an already small population...well...doesn't take much to figure out why there aren't more companies with dedicated vegan production facilities since they can share equipment and keep costs reasonable. Unless, of course, you wouldn't mind paying $5 for a Clif bar someday just so they can open a new facility just for us
In the end, it isn't creating a dependancy on more animal by-products, it isn't willingly supporting the use of animal by-products for manufacture if you're buying the vegan ones, so unless you're looking to be a purist OR have severe allergies that could be life-threatening, there isn't much to be concerned with over allergen notices these days. It's just the way things will be - prior to 2008, such notices were optional, but now they're mandatory on most foods, which is why you'll find them on items that may not have had them in the past.