Native apps have high install friction and a lot of nasty cross-platform tradeoffs. Even though there's always a cohort here (rightly) commenting on how much of a step backwards the web is for GUI app development, one has to admit that we are past the time where a truly cross-platform, install-less native app SDK can be created and cross the chasm to universal adoption. Web tech is what we have, worse is better, yada yada.
Accepting that reality, one of the implications of the web and cloud-storage is that the server component tends to be heavy. While it's convenient for users to have their data centralized in the cloud for consistency and access on multiple devices, this does incur some significant overhead in terms of account managment, authentication, and database hosting.
The thing that I find really cool about local-first web development is that it reopens the door for hobbyist and micro-ISV apps that can served cheaply as static files, where the customer pays for the compute and stores the data. There are lots of potential micro-apps, which don't require network effects or large data storage, that could be built this way and avoid incurring significant ops overhead for the developer. Obviously it runs counter to user expectations today, but I think a lot people might also appreciate useful apps that don't have $5/month subscription as table stakes just to keep the lights on. Also, it doesn't have to be a binary proposition, there could be accounts/sync functionality optional. Most of all, as a developer, it's exciting to have the ability to try out an idea, with optionality to ramp it up into a full SaaS, or scale it down without an abrupt rug-pull on the early adopters.