What are the benefits of storing columns in JSON instead of traditional tables? Are there any benefits in using JSON(B) over traditional table structures?

Imagine having a table structure like this:

 create table table1 (
        t_id int,
        first_name varchar(20),
        last_name varchar(20),
        age int
    )


What if you stored the same columns inside a JSON(B) field like this:

{
    "first_name":"name",
    "last_name":"name",
    "age":2
}


and have a table like this:

create table table2 (
    t_id int,
    attribute jsonb
)


Correct me if I'm wrong, but since both variants are causing a row to be completely rewritten if there have been any updates or deletes on that row, then both variants are identical in that regard.
If you really want to be able to add as many fields as you want with no limitation (other than an arbitrary document size limit), consider a NoSQL solution such as MongoDB.

For relational databases: use one column per value. Putting a JSON blob in a column makes it virtually impossible to query (and painfully slow when you actually find a query that works).

Relational databases take advantage of data types when indexing, and are intended to be implemented with a normalized structure.

As a side note: this isn't to say you should never store JSON in a relational database. If you're adding true metadata, or if your JSON is describing the information that does not need to be queried and is only used for display, it may be overkill to create a separate column for all of the data points.
Check this one for detailed explanation