Hashcash, Bitcoin’s predecessor, was created to solve email spam: https://en.m.wikipedia.org/wiki/Hashcash https://en.m.wikipedia.org/wiki/Hashcash Having use

Hashcash, Bitcoin’s predecessor, was created to solve email spam: https://en.m.wikipedia.org/wiki/Hashcash https://en.m.wikipedia.org/wiki/Hashcash Having users to pay actions make spam unprofitable, as spam relies on tragedy of commons and abusing public goods. This is why there is so much less SMS spam compared to email spam.