> How often do you really do things like this though?

All the time. Some examples:

* ct, : "change up to comma", useful for replacing a function argument.

* ya" : "yank around '"'", copy the string literal the cursor is currently inside.

* ci( : "change inside '('", useful for changing the condition in an "if" statement.

* da{ : "delete (i.e. cut) '{'-delimited block", useful when changing the structure of if/else blocks.

I agree that these commands may sound obscure, and many Vim users use the program for a long time without using them (I certainly did). But when you start using them, you find that these composable editing commands correspond really well to many of the logical editing actions you perform.

I don't use vim, but this feature seems mostly useful for deleting things within marking characters, such as " and ', which I do surprisingly often. (But not often enough to learn a shortcut to do it)

Not that specific example, but you'd really be surprised by how useful some of these things are. For example you can do a `di[` to delete everything inside an array. Or `ci"` to replace everything inside a string.

Very often, actually. It's something that pops up quite a lot when editing code, and you want to remove/change a chunk of text.

In the very comment you're replying to I already said "stuff I use constantly".