As said in other comments, this is because speedtest.net largely tests within your isps' network, not the path off their network to other ISPs or to netflix/net

As said in other comments, this is because speedtest.net largely tests within your isps' network, not the path off their network to other ISPs or to netflix/netflix like services. To put this another way, speedtest is kind of lying to you in favor of your isp, which is the source of their funding.