The vast majority of crypto projects in top 100 by market cap are not like UST/LUNA. The demand for them comes from speculation about future utility, but there is no unsustainable market-beating yield to entice people to deposit new money.
And as an aside, not being in compliance with SEC regulation does not in any way make a project scammy. Being non-compliant with SEC regulations could be the case with LUNA, and still be entirely incidental to it being scammy, as it is possible to operate with no deception and without exploiting any one - which is an essential component of any scam - and still run afoul many SEC regulations.