Consider a microservices architecture (for the sake of example), where a user sign up needs to create an account in three services: auth-svc, avatars-svc and emails-svc.
Your options to do it are either an event-sourcing architecture where your services have to orchestrate together via somewhat-awkward message-passing, or write another reconciling service where you write the logic more-or-less directly, but with a ton of code-overhead to make the execution reliable.
Waymark would help with the second approach, because it soaks in all the durable execution complexity, and gives you a way to just write the logic code and handle the edge cases - with a fraction of the code and systems you'd need otherwise.
I'd even dare to say - a tool like waymark, the second approach is pretty much impractical altogether, hence why the event sourcing microserivce architectures dominate today.
But, yet again, that's just one example of where waymark would be useful. If you can write the code where you can split the orchestration logic from the execution of the individual side effects - then with waymark your orchestration code can be just the logic you need, without the extra steps to persist the progress - thus making it easier to reason and mental model simpler.
[1] https://docs.rs/tower/latest/tower/