S/C and S/G are participation classes, not spectator classes. They are the biggest classes at any national event or divisional event for that matter. They aren't going anywhere. If you don't want to watch them, don't. There are 1,000 other things to do at the track when those cars are running. It's not like there is anything else that could be running in their place that would keep spectators in the stands. Hell, they won't stay to watch the Factory Stock cars, Alcohol cars or Pro Stock. 90% of the people in the stands couldn't tell you what a throttle stop is, so to assume people are not watching because of the throttle stops is flat out laughable.
IMO, the decline in attendance in Divisionals started when they quit doing divisional Top Fuel championships and the proliferation of National Events. Divisionals were a big deal when there were only 8 or 10 National Events a year, now that there are 24, not so much. Divisionals still exist because they are profitable for the tracks and NHRA, mostly because of the big participation classes like S/C and S/G paying all of that back gate.
Lastly, if you all had your way and got rid of the throttle stop classes, it would be absolutely devastating for 1,000s of racers, tracks and the aftermarket suppliers, many of whom would have to close up shop without selling parts and support to the super category racers.