That's not really what I mean.
The 15 minute thing is an estimate. It's not like you spend 14 minutes with someone and there's zero chance, and 15 minutes is 100%. 15 minutes is where the percentage likelihood goes above something, let's just assume 50% likely of passing it on. At 10 minutes it's maybe 20%, at 1 minute it's maybe 1%.
So, lots of short interactions with infected people, will increase your chances of getting it. Which is pretty intuitive.
The original question was, does the actions of others impact the risk of you getting it. If their actions increase their likelihood, then it will obviously increase yours.
To use the R value example, without restrictions, this has an R of about 3.0. Meaning that each person will, on average infect 3 people, that rolls into approx 59,000 people in 10 days. For reference, common flu has a, without restrictions, R of about 1.3, which after 10 days means one person infects 14 people
Wiith restrictions, we get Covid down to 1.0 or below, so it's either stable or regressing depending on that number. If people don't follow restrictions, that number can obviously explode and affects everyone's chances of getting it.
Well like I said, it's just a practical matter of whether fleeting, practically unavoidable interactions are actually risky to some extent. If they are, then that's a bit of a problem for the idea of allowing people to bear risk at their own cost. If not, then to me it seems like the risk of catching it from strangers is something a person can control for.
Even being close to someone for as little as a minute is something someone can easily avoid if they want to.