Looking for an explanation on rear suspensions

[Harry]

Back around 1970 I think it was Mickey Thompson who welded the rear solid to his funny car frame. Everyone else followed. Coil overs eventually came off all 4 corners. Not only was the rear mounted solid but in 73-74 the front axle also became solid in various ways since NHRA didn't allow the front to be solid at that time. Keep in mind transmissions went from automatics to the Crowerglide clutch / Lenco 2 speed during this period.
My thought is why Pro Mod and Pro Stock continue to run coil over shocks at these crazy speeds. Isn't it time to mount that rear solid? If not, why not?

 

[SoCal Racer]

I'll hazard a guess but I'm no expert. Early FEDs quickly overpowered sprung suspension almost universally ran no suspension on the rear axle (the Magicar being a notable exception). For them the light weight of the car and flex of the long wheelbase chassis acted as all the suspension they needed. Early funny cars were heavier and shorter than dragsters and did not have these factors working in their favor, and neither do Pro mods.