Yeah I've started using them as it's easy to jump to a section to work on it. I generally know where they sections are but it's just an extra thing to use if it's needed.
I am glad I am not alone. I also like to use a different colored marker for notes and reminders, (add gang vox here, or widen space here) It is definitely a handy tool!
I use them to mark verse/chorus etc.
Also to mark any points the band wants something to happen (sample/glitches/freq changes)
And to mark any point I get an idea for it so I can come back later and do it.