Well, you don't have to literally count them, you use the spatial reasoning hardware built in to your retina and visual cortex to just see that this bit of code is further over to the right than that bit of code. But of course that only works for pieces of code that are small enough to fit in your field of view.
All code pieces should be small enough to fit in your field of view :)
Try to tell that to my current client :-(
If boundaries exist they need to be clear. One shouldn't have to count the tabs that make up the level of indentation.
Its already a challenge reading code. Counting invisible tabs makes it even worse.