https://docs.oracle.com/cd/A64702_01/doc/server.805/a58241/ch_ov.htm

You're using an example from the 8i docs?!

If you want to dig into these, I'd recommend reading something more up-to-date:

https://docs.oracle.com/en/database/oracle/oracle-database/18/adobj/applying-an-object-model-to-relational-data.html#GUID-5D527C3A-6B6F-4C8E-A3F5-93340737F8B0

Anyway, the reason to use object views is to map your relational tables to an object-oriented application's classes. So this is your ORM layer. Instead of some other tool.

This gives you full control over the SQL. Which can lead to better performance. If you build it right ;)

But if you use these for writes, you'll need to create instead-of triggers as you say. Which if you build it right, can scale well. But is super easy to make a mess of.

OO-based applications are widespread. So the concept of ORM mapping is here to stay. And object views are one way to do that.

I've not seen them in the wild though. And I'd rather build a series of PL/SQL APIs that send and receive objects instead of object views. Something I have seen done successfully.

That said, JSON is increasingly becoming the standard format for data exchange. So building APIs that transfer these documents is a better bet.