That doesn't even seem to be the issue here.

Which is weird. In my humble layman's opinion, an ICO looks an awful lot like a security offering, while a staking protocol doesn't.

Compare the simplified statements "Buy my token! It's going to be great in the future!" with "Let's pool our money and execute an agreed-upon protocol where those who have the most get more". Why is the SEC wasting time by going after all the weird ones before the easy pickings?

It was however an ICO does not make it inherently a security. Per the SEC:

    ICOs, based on specific facts, may be securities offerings, and fall under the SEC’s jurisdiction of enforcing federal securities laws.

And I think it's ultimately up to the courts (unless the SEC eventually gives a definitive answer) to determine what specific qualities make an token offered via ICO into a security, especially because what qualifies as an ICO really kinda varies and how they are structured also really widely varies.

https://www.sec.gov/securities-topics/ICO