This was one of the reasons given, at the time, for why Netflix created fast.com. It's served by the same infra that does their streaming, and is thus difficult for isps to game. That is, it'd be hard for them to do some hack to make fast.com numbers without also benefiting Netflix streaming performance in the bargain.

Actually I thought Netflix had already acquired Ookla / speedtest.com, so I was surprised to see this headline. But it looks like this was just the Mandela effect.

That said, why didn't Netflix acquire the market leader in this space? Creating their own seems way less useful, since network effects are the whole point.