Having branch offices with 100 Mbps (or less!) Internet connections is still common. I’ve worked tickets where the root cause of network problems such as dropped calls ended up being due to bandwidth constraints. Get enough users streaming Spotify and Netflix and it can get in the way of legitimate business needs.
Sure, there’s shaping/qos rules and dns blocking. But the point is that some networks are no place for personal consumption. If an employer wants to use a MITM box to enforce that, so be it.