People will continue to drive at speed, regardless of the punishment.
Sure, just as some will continue to kill regardless of the punishment. However, others will decide that the utility gained, whether by killing or speeding or whatever, is simply not worth the penalty if caught.
Many here have already stated the same as it pertains to their own driving and riding. Toughening penalties together with improving odds of being caught will act to increase deterrence. There will be a point of diminishing returns, but deterrence will generally increase with tougher penalties and improved odds of detection and application of those penalties, despite the presence of a those who will not be deterred by any penalty.
Also, if people's driving habits have changed as a result of stiffer penalties, that is no guarantee that the roads are now safer, in the sense of fewer accidents and fatalities. They will continue to occur
Of course collisions will continue to occur, but collisions at lower speeds tend to be less damaging than collisions at higher speeds. In the cases of first Ontario, then Nova Scotia, and most recently British Columbia, implementation of tough racing/stunting/extreme driving laws has in each locale been followed by a marked reduction in fatality per km driven rates far beyond any changes seen elsewhere. Three completely different locales, with three different implementation dates, each seeing the same outcome following implementation.
If you doubt this, please visit the "Fallen Rider's" section of this website, or listen to traffic reports during rush hour.
Speeding does not equal accidents, a failure of one's skill as a driver does.
There is no such thing as a perfect rider or driver. Drivers and riders will fail more often than they might want to admit. Speeding reduces your margin of error recoverability and crash avoidance. It reduces your chances of reacting in time to the errors of others. Braking distance increases exponentially with speed, and increasing speed also makes it more difficult to deviate from your path to avoid something in front of you. When you do crash, speed makes the outcome more severe.
I have read the Fallen Riders section. I have also read the various police and media reports on most of the crashes in that section. Excess speed is a causation or aggravating factor in many of those crashes.
This is why we must drive and ride keeping a margin of recoverability available to us, whether to be able to avoid the crash altogether or to at least be able to mitigate the severity of crash if we can't avoid one.