I understand that this was the mentality in "The Art of UNIX programming", and it is really powerful. The problem is that UNIX never provided a good way to compose programs that need to exchange more than text.
As a result, the outputs of a UNIX-like system are great for programmers but terrible to use by everyone else. For example, if you need an interface that display a nice button to execute a function, you're out of luck with UNIX. The more detailed the interface, the more complicated it becomes. That's why OO has become the de facto way to create user friendly UIs.
It's true. Parsing is a pain and a source of security holes. There are a lot of people trying to do things with structured data over pipes. But there are a lot of ways to do it wrong, and consequently it hasn't caught on much. I've been working on some code for awhile which is too much to go into here, but it's trying to solve this problem of text-over-pipes being too limited, without introducing the tighter coupling of OOP.
You could argue that JSON web services are basically this, but in practice I don't see that they're used in a strongly compositional way.
However, the funny thing is that OO arguably isn't the way we create interfaces anymore. We create interfaces by sending domain-specific languages like HTML and CSS over the network.
Although I guess you could argue iOS and Android interfaces are created with OOP, and I won't deny that it's a successful paradigm there. Objects make a lot of sense for things like games and writing CAD programs and so forth. The "modeling" works in those domains. It doesn't really make a lot of sense for server software. Basically OOP is a domain-specific language IMO.
As a result, the outputs of a UNIX-like system are great for programmers but terrible to use by everyone else. For example, if you need an interface that display a nice button to execute a function, you're out of luck with UNIX. The more detailed the interface, the more complicated it becomes. That's why OO has become the de facto way to create user friendly UIs.