Disclaimer: I would only call my skill level as intermediate and would yield to any more senior developer here.

It's not a hard and fast rule, but you can usually write it without the else and in fewer lines.

So take for a very contrived example a function that needs to return a non boolean value for a boolean test. A use case could be if you need to figure out a string argument for another function, such as you need to determine if you need to keep the "first" or "last" duplicate in a dataframe (I'm thinking about pandas's df.drop_dupliactes method).

Continuing with the drop_duplicate thing let's say we have a dataframe we need to de-duplicate but for some reason if the overall length of the dataframe is even, we need to keep the first duplicate and if the dataframe length is odd we keep the last. I don't know why we would, but that was a very particular request from the customer and we need the money to buy more Warhammer figurines.

import pandas as pd

# With else statement
def foo(x: int) -> str:
    if x%2>0:
        return "last"
    else:
        return "first"

# No else statement, shorter.
def foo(x: int) -> str:
    if x%2>0:
        return "last"
    return "first"


#import dataframe, deduplicate
df = pd.read_csv("c:\\path\\to\\data.csv")
dedup = df.drop_duplicates(keep=foo(len(df))

Here's an essay that goes into more detail