How does the Python identity operator work?

Question

I’m starting in Python and would like to ask a question based on the code below:

Case 1

x = 5
y = 5

print(x is y) # retorna True

Case 2

x = "carro"
y = "carro"

print(x is y) # retorna True

Case 3:

x = [1,2,3]
y = [1,2,3]

print(x is y) # retorna False

Why does this happen? I have already researched this subject and know the identity operator is compares objects and their memory location and not their values - what is done by the operator ==.

But even so, I don’t understand for example why integers and strings are allocated or pointed to the same memory location and lists not for some internal Python reason, if that is indeed true.