This is getting a little ridiculous. Multiple people have explained the TaG/multi-engine class thing to you on your other 3 threads you posted this week, but for some reason you’re not understanding.
It’s pretty simple; multi-engine TaG racing was too expensive, so people wanted single-engine. Now each engine manufacturer is pushing their product. IAME seems to be producing the best product right now, that’s why many series are running their product.
If you were actually involved in the sport other than being an outside observer, you would have a better grasp on the series, what their future plans are, how you can make an informed buying decision on an engine, and what series is best for you.
SKUSA has the west coast covered, WKA/USPKS/F-Series have the midwest/east coast covered. Find out what their rule sets are, visit your local club, buy a used kart for $1000 and go have fun. That’s what will “fix” karting. Sitting around on the internet complaining about something you have no frame of reference or experience with isn’t helping the sport.