Speakon is not necessary for 300w amps like super bassman or svt. 500w is a Grey area, it is really the 800w+ where speakon is needed. Back before speakon most amps had 1/4" only, and banana plugs for the bridge outputs, where 1/4" might be a bit of a bottleneck. Higher power PA amps had spade lug terminals and banana terminals.
While speakon has more connection real estate than 1/4" (just about everything except RCA does), really the twist lock feature, and 4 conductor capability are the main advantages in the moderate power ranges we tend to be in (300-800w), and only GK uses the 4 conductor feature with their amps that have the dedicated 50w HF section that works with their cabs.
Back in the late 90s, we rewired all of the Yamaha club IV series PA cabs to 4 conductor speakon, ditching the passive crossovers and biamping them with qsc PLX series power amps, for our concert sound engineering program at the local college. We got much more out of those cabs than expected that way, but we also had to wire up dummy proof output panels on the back of the amp rack to do so.
I never bothered to go speakon with my bass rigs.