Why is sys.stdout adjustment needed to print Unicode in Python?

Question

I scraped some data from the web using:

import requests
from bs4 import BeautifulSoup


def get_lines_from_url(url):
    response = requests.get(url)

    if response.status_code == 200:
        soup = BeautifulSoup(response.text, 'html.parser')
        lines = soup.get_text("\n").strip().splitlines()
    return lines

while printing them with:

all_lines = get_lines_from_url(link)
for line in all_lines:
    print(line)

i encounter UnicodeEncodeError: 'charmap' codec can't encode character '\u2588' in position 0: character maps to <undefined>

I printed the encoded version of each line with:

for line in all_lines:
    print(line.encode('utf-8'))

The culprit was a line containing b'\xe2\x96\x88'.

I did some research and found that all lines print when i include sys.stdout = codecs.getwriter("utf-8")(sys.stdout.detach()) as in:

import sys
import codecs
# other imports...

# `get_lines_from_url` declaration...

sys.stdout = codecs.getwriter("utf-8")(sys.stdout.detach())

all_lines = get_lines_from_url(link)
for line in all_lines:
    print(line)

What does sys.stdout = codecs.getwriter("utf-8")(sys.stdout.detach()) do? why couldn't Python print b'\xe2\x96\x88' directly?