I wrote some software at an automated trading firm that would do the subset of "parsing ticks and maintaining order books" sufficient to map ticks to symbols, and no more work than that. My code was pinned to one core and spun waiting for an expensive network card to DMA some ticks into memory, then when ticks we cared about were found it would load them onto one or more queues. Each queue corresponded to a different thread spin waiting on its own pinned core.

So one use case is "transforming ticks into trading decisions slightly faster than you otherwise could"