Sports and porn are just different, people watch sports to watch top athletes play and porn uh well.
People watch porn when sex isn't directly available whether in a relationship or not ( your significant other isn't going to be horny and willing at the same time as you every time you are ).
The argument only really makes sense if we're talking about pro E-sports players, it becomes a lot sketchier when we don't and especially when we talk about story-driven games.
Very few Streamers are actually top players and they're not the biggest ones either.

Quite a lot of Twitch is just drama too and like a reality tv-show with people who have insanely huge egos and have mental breakdowns about everything.
Twitch Streamers themselves on a whole aren't normal people, most of the big ones are adult young teenagers.
They got popular when they were teens and they never grew up because they've lived on Twitch, it's pretty apparent when you compare them to actual adults who weren't kids when they started streaming.
I dunno if I want to name names because people get mad if you say anything about their favorite Streamer, but holy hell.
The toxicity and brain rot that is Twitch is something the Streamers themselves have essentially created and perpetuated.

I watch Twitch too, not very often and only a very limited amount of Streams but I have it on as background noise and in regards to FFXIV I just like to see peoples reactions to it.
I am not insanely attached to them tho it's the same with Youtube too I've stopped watching people entirely because they just started to frustrate me.
I dunno why really, I just enjoy it.
It's like how I can't understand why people get so upset and triggered by sexualized content while I enjoy it, who knows?
You enjoy what you enjoy or don't enjoy what you don't enjoy, there's not always some deep reason behind it.