As transactions are free on EOS when an account has sufficient CPU and NET, it is important that there is sufficient activity on the EOS chain in order to keep the requirements on CPU and NET sufficient high. Otherwise nobody would need to stake (and lock) EOS when using the EOS blockchain. It would also be easy to spam the blockchain.
Interesting/plausible conclusion.
RE: EOS inflates their blocktivity stats by massively sending batched transactions with a value of 0.0001 EOS