Many of these books claim that by creating these abstractions, in this example Person, you can “re-use” them in other projects. However, in 15 years of my professional experience, I have hardly seen many (or any) examples of such abstractions being used across projects in a useful manner.
At one point, I started creating a class library of these abstractions that I could share across projects. After a little while, that class library ended up being bloated with lots of unrelated abstractions and versioning it across different projects ended up being a nightmare. If you have done this before, you may relate to this story.
Once I was engaged as a consultant for a greenfield project, and in the introductory session, the data architect of the project walked me through tons of UML class diagrams (more than 50 pages). Every class was inheriting from another class and eventually, they all led to a class that was called “Thing”! No joke!