OP, that's a very "posh" concern of your friends.
It all depends on circumstances.
It made me think of my recent hike to Machu Picchu. Already, after the first day, all nine of us, complete strangers from five countries, age 20-54, gathered in a tent, sharing snacks from a plastic bowl and passing a bottle of whiskey around, no glasses. It was dark and freezing cold outside, and there was no water to wash your hands after having a pee.

When you bring the large tin of toffee popcorn to work, also bring a mug or food scoop that people can use to fill a coffee-filter paper bowl. Keeps clean hands from getting sticky, and discourages dirty hands from touching everything.

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<hr>The rationale being that someone's urine stained hand could contaminate the entire batch.<hr></blockquote>
Contaminate it with what?

yeah, there's some truth to it, bowls of peanuts in bars have been analysed and lord-knows-how-many samples of pee have been found on them thanks to those who don't wash.
IMO, it's one to file under paranoia, however.

My neighborhood bar provides little bowls of peanuts or snacks to each patron, then discards them when said patron leaves. They also have drinking straws that are wrapped in plastic in such a way that the bartender snaps off the bottom portion of the wrap and inserts the straw into the glass without ever touching it. Paranoid, in my opinion.

#12 - I agree about the stereotype, and offered up the suggestion only to encourage OP to bring in the great treats. I personally have no worries about the shared dried snacks dish in an office or small party group. At a restaurant or bar, thought, I want to only share food with people I know.
E-Boi, yeah, double dipping's an issue. If possible I try to take the food item and turn it around end dip the unbitten side into the dip. It's easy w/ like a breadstick but not as easy w/ shrimp.
Midwesterner, now that you mention it my mom used to do that when she had her girlfriends over. She'd pour bridge mix into a gravy boat (or something that looked like it) and they'd ladle out the mix onto a cocktail napkin. I totally forgot about that.
ManchVegas, I believe that trick of your mother's was less about the ladies pawing through the shared bridge mix, and more about comfort. I.e., with individual portions, they didn't have to hunch over the common bowl.