Well, yes, but what does 2% failure rate per year even mean when it's presented independent of a number of uses per year? I mean, without knowing what number of average uses were used to calculate "2% failure rate per year", it seems like somewhat of a misleading statement, as I'm reasonably certain (let's say at least 90%) that it's not intended to reflect that condoms become more protective the more chances you have to use them.
I feel like I'm missing something basic here that would let me see why it's a useful piece of information on its own.
I agree it's misleading. That's why I'd prefer a metric like this, where the precise definitions you use don't matter if they are the same in both the numerator and the denominator as constant factors would cancel out.
P/S/A: There are single sentences which can create life-changing amounts of difference.