Player cams require a lot of bandwidth, hardware on the side of players, as well as significant work on the side of the broadcast team.
The way Riot did them during the Stage 1 Masters (unless I'm gaslighting myself...) is that they sent each of the players in the event a Raspberry Pi, which is a tiny single-board computer that runs on Linux, with a camera attached to it. The players connect it to the internet and it essentially streams back to Riot's production setup and they use those streams live whenever they need to. The reason why the camera is its own device running on a RPi is because video processing takes some processing power and bandwidth, and they don't want it to affect the players' performance in games. This is the same tech that the Overwatch League uses.
It's also a lot on the side of the players as well as the broadcast team, which is why the more skeleton crew of NSG and other regions don't use them, as they already have complex online setups and it's expensive to host a stream at the scale that people expect from a Riot-sponsored circuit.
So, why not just use webcams, like your region likely does? Because most of them look like shit and it's still a ton of extra work. And really: who cares if people enjoy it a bit more; ultimately NSG are just a contractor to Riot for the VCT NA circuit and money is always on the mind. You're already tuning into the streams to see the teams compete, why spend extra money to set up player cams and other gimmicks? NSG have nowhere near the resources that they need to be on par with Riot's own seasoned production team, and they're stretched thin due to the numerous streams they have to maintain due to the size of their open brackets.
There are other nuances in this, but at that point, we're delving into business and that's a whole 'nother world entirely.