No, it's not thanks to legal precedent. Legal precedent is when a case establishes a rule that can be used in future cases, and is, in effect, creating a new law.
This is setting an example, where if you do something that screws over a lot of people in a very small way, you can't get away with it just because nobody is damaged enough to care. Instead, all the aggregated damages are counted together, and that tends to be enormous.
And it's not really that big a problem that 99% of the people in the class are too lazy to care they've been screwed. As long as they can get together a few people that care, and get lawyers to represent them, then they can bring a class action on behalf of all of them.