Why can your car do twice the maximum speed limit? Are they trying to kill us?

The maximum speed limit I have ever driven in is 70 mph. Some speed limits are 65, some 55, some 45 mph. But for some reason, most automobiles are capable of traveling in excess of 100 mph. Why? Are automobile manufacturers trying to kill us? If it's not legal to drive over 70 mph in most states, why do vehicles need to travel 50 or 60 or 70 mph faster than that? Do"they" want us to die? Now I'm not sure who "they" are. But there is no logical reason for a vehicle that is designed for driving on public roads to travel at these high rates of speed.

When I was in college and being irresponsible, I once drove my Honda Civic 115 mph on a state highway. This was a 4 cylinder car with only 106 horsepower. It could certainly go faster, but that's as fast as I was willing to push it that day.  Some time after that I owned an Acura TL. I got it to 130 mph on a back country road once. This was a v6 with 270 horsepower. It could certainly go faster, but that's as fast as I was willing to push it that day. Both incidents could have easily killed me.  When I look back on it now, I can't believe how foolish I was. But the cars provided the means for me to take my foolishness far beyond anything I should have been able to accomplish.

If the highest speed limits are around 70 mph, why make the vehicles capable of 140? Why not limit all non track driven automobiles to 75 mph. This would still allow some room for state troopers to meet their quotas writing speeding tickets.  But it would save a lot of lives and serious injuries. This would be particularly helpful to save all those motorcyclists that do 150 mph on the highway from endangering themselves and others. But for some reason this doesn't seem logical to vehicle manufacturers. Sometimes I wonder if we are being set up for some big experiment. As if "they" know that human nature will make people do what I did as a youngster (push the limits).  Is it population control? Is it some kind of a sick joke being played on us?  

Just because vehicles are designed this way and this is what we are accustomed to, it doesn't make it right. If our government really cared about keeping us safe, why would they allow us to be on the roads with people that can simply push the pedal harder and kill us and our children? Especially when they know that people drive under the influence all the time. But then again, this is the same government that encourages and lets you buy guns designed to kill people. We are all conditioned by our environment. But I am not one that accepts that things have to be the way they are. So the next time you see someone fly by you at 100+ mph, ask yourself this simple question and give it some serious thought. Why is that even possible? What say you epic venters?