why does python dataFrames' are localted only in the same machine?
Pandas doesnt allow you to distribute the datframe to mulitple machine at it own. It is good to us when you have data that

Fit in Memory (RAM)
Fits in Disk

So, it works well when you can have data that can be handled with single machine. But when the data and processing needs grows, you want to move to libraries that store and handle distributed/parallel processing of dataframes. The concept of dataframe is common in these libraries, but implementation differs to provide distributed processing power. Two good examples are

Dask, it is typically used on a single machine utilising multiple cores/thread by multiprocessing/multitasking, but can also runs well on a distributed cluster.
Apache spark is mainly used in cluster mode on multiple node, hence distributed data processing framework. (but it can be used on single standlone machine as well)

Update:
You asked that

DataFrame CONCEPT is the one that is not distributed, however R and
Python have other concept to do distributed computation

Dataframe don't needs to be non-distributed or distributed, it is a concept , DataFrame is a 2-dimensional data structure with columns that can have different types and it is so easy and efficient to query,summarise and manipulate that it was adopted in many Data-oriented Programming Paradigms and libraries. So, utilising and manipulating these dataframes can be done in distributed manner as well to handle Big data. Spark is just an example of Distributed data processing framework, which can be used with many languages including R and Python
I'm reading spark the definitive guide in which it is said :

Python/R DataFrames exist on one machine rather than multiple machines... this limits what you can do with a given DataFrame to resources that exist on that specific machine..

therefore, I wonder why Python's dataFrame can't spand to multiple machines ? and if that means that python's are not distributed ?
Update
does Python/R have an equivalent distributed DataFrame like Spark scala/java??DataFrame