Why might packaged pineapple contain egg, soy, peanut, fish, milk, sulphites, tree nuts, sesame, crustaceans, shellfish, mustard seeds, wheat?
Although it doesn't explicitly say so, that's allergy information. It's just been processed in a place that also (potentially) processes those things, so it potentially contains a trace amount, which could be bad if you have a really sensitive allergy. It won't contain enough of those things to matter for any other purpose.

Often labels like that are written along the lines of "processed in a facility which also processes..." to make it a little more clear. The lists aren't usually that long, either; most facilities don't process everything. But as pointed out in the comments, a grocery store is a lot more likely to just have a single kitchen that possibly handles all kinds of things.