One does not automatically earn a return just by staking eth. A validator with a node has to be operated which performs the validation and block proposal functi

One does not automatically earn a return just by staking eth. A validator with a node has to be operated which performs the validation and block proposal functions, and money is only made when those activities are performed. The eth that is deposited is not an investment - it is a bond for good and honest performance of the work. Now, there are services that perform those activities on behalf of others, and some of those arrangements could possibly be labeled as securities, but on it's own, at the base layer, participating in eth's proof of stake system is not a security.