I mostly disagree, as I see little need for smart contracts as opposed to 2nd layer apps for this. However, there are some advantages for smart contracts, and I'll discuss those in my next post on this subject.
I see your point about smart contracts not requiring that there be additional API servers to support the 2nd level apps, but I see this as doing no one any real favors.
This forces 1st layer nodes to support apps that they shouldn't be forced to support and it forces those apps to be supported in a less secure and less performant way. It also destroys scalability, since all the apps have to fit into a "one size fits all" node architecture. And don't even get me started on the increased difficulties of paralellizing the workload of the smart contracts.
And it's not like the smart contract developers really get a free ride either: the blockchain has to somehow pass on those extra costs to the smart contract's developor or users, or else the whole platform will just be taken down when smart contracts abuse those scarce resources. While the smart contractor developer doesn't necessarily pay those costs (depending on the smart contract platform), their users do, and this can have real impacts on the adoption rate for the developer's smart contract.