I worked in the networking group for a cloud computing company. You've heard of them. We didn't charge for (some) DNS traffic, so some customers figured out how to use DNS as a transport mechanism to skirt around paying data transfer fees. It would essentially be a DoS attack which affected EVERY customer, so a few could save tiny fractions of their overall spend. A peer team of mine had to deal with the mess. That team had > 100% annual staff turnover, because they just made the oncall staff deal with the problem every time it showed up rather than ever solve the core issue of having a DoS vector masquerading as a feature.
Wouldn’t the solution be to just start charging for excessive DNS traffic?
Potentially yes, but that's a business decision which the on-call developer cannot deal make on behalf of the business.
There's a lot of stuff the dev team can do that are not strictly business decisions though. Rate limits, QoS, etc.
Those can be business decisions too though. It depends on whether or not the real / lucrative customers will notice, or maybe the noisy customers who will be all over twitter because a dev figured they'd make a big change like this on their own.
Throttling and tiering can definitely affect more people than you might suspect (like spiky services) and considering data and use are important.