Some systems do not have the luxury of running Linux. In fact, some systems have no operating system at all. In the embedded computing world, they are called bare-metal systems.
Bare-metal systems usually run a single application; think of microcontrollers, digital signal processors, or real-time dedicated units of any kind. It would be wrong, however, to assume that those application-specific applications are simple: they often are sophisticated little beasts. Hence the need to debug them, and of course, to trace them in order to highlight latency issues, especially since they're almost always required to meet strict real-time constraints.
Since Linux is not available on bare-metal systems, LTTng is unfortunately out of reach. LTTng's trace format, the Common Trace Format (CTF), is, however, still very relevant. Because CTF was designed with flexibility and write performance in mind, it's actually a well suited trace format for bare-metal environments.