Driver and passenger airbags directly protect the purchaser, or the family of the purchaser. The purchaser cares specifically about these people and will be more likely to pay to increase their safety. In a sense, it's an easy sell.

This system doesn't increase the safety of someone dear to the purchaser and therefore seems to be less attractive, unless there is some other compensation, e.g reduced insurance rates.

But any normal person wouldn't want to hurt others if it's easily avoidable?

Sure, but people are only limitedly altruistic (see the tragedy of the commons). If this system was free, then it should undoubtedly receive a huge uptake. But it's not free! So is there a way to encourage uptake without compulsion? Reduced insurance premiums could be one way. Are there others? Reduced car tax on vehicles with pedestrian-safety features installed?