为什么经过线程池处理了Python爬虫效率还怎么低呢？

Question

我用线程池，但感觉没起作用

import re
import requests
import json
import os
from concurrent.futures import ThreadPoolExecutor
from time import time
ltime = int(time())


# 拿到播放首页的页面源码
def get_sourse(page):
    # url不要写错了，不要带后面的参数，参数已经被封装到了params字典里！
    url = "https://www.bilibili.com/video/BV1Kh411r7uR"
    headers = {
        "User-Agent": "",
    }# ua需填
    params = {
        'p': page,
        'vd_source': '8d74638d8c4f1428cf1da9c50d5455f6',
              }
    resp = requests.get(url,headers=headers,params=params,stream=True)
    resp.encoding="utf-8"
    return resp.text


# 拿到源码中的嵌套的视频、音频链接
def get_dv_url():
    # 这里的正则对于不同的视频可能会不一样，要注意一下！
    pattern = re.compile('window.__playinfo__=(?P<playinfo>.*?)</script>', re.S)
    video_html = pattern.finditer(get_sourse(i))

    # 这里直接用迭代器__next__()方法取值，不用for循环
    playinfo = video_html.__next__().group("playinfo")
    # print(playinfo)
    result = json.loads(playinfo)
    # print(result)
    videourl = result['data']['dash']['video'][0]['baseUrl']
    audiourl = result['data']['dash']['audio'][0]['baseUrl']
    return videourl,audiourl

# 下载音视频
def download():
    headers = {
        "User-Agent": "",#ua需填
        "referer":"https://www.bilibili.com/video/BV1Kh411r7uR?p=1&vd_source=8d74638d8c4f1428cf1da9c50d5455f6"
    }
    resp_video = requests.get(get_dv_url()[0],headers=headers).content
    resp_audio = requests.get(get_dv_url()[1],headers=headers).content
    # 异常捕获用于当要创建的目录存在时跳过创建目录
    try:
        # 创建目录
        os.mkdir(f'D:\\video_data\\zhiyuanjsnx\\{i}')
    except FileExistsError:
        pass
    # 判断文件存在并跳过创建写入文件
    isExists_1 = os.path.exists(f"D:\\video_data\\zhiyuanjsnx\\{i}\\{i}_video.m4s")
    if not isExists_1:
        with open(f'D:\\video_data\\zhiyuanjsnx\\{i}\\{i}_video.m4s',mode="wb") as f:
            f.write(resp_video)
    isExists_2 = os.path.exists(f'D:\\video_data\\zhiyuanjsnx\\{i}\\{i}_audio.m4s')
    if not isExists_2:
        with open(f'D:\\video_data\\zhiyuanjsnx\\{i}\\{i}_audio.m4s',mode="wb") as f:
            f.write(resp_audio)


if __name__ == '__main__':
    page = int(input("请输入你要下载的集数："))
    t1 = time()
    # 创建线程池
    with ThreadPoolExecutor(50) as k:
        for i in range(36, page+1):
            k.submit(download())
    t2 = time()
    print("此次程序执行耗时：",t2-t1)