Why are oval race tracks made?

Some are oval, some are round, and some are tri-ovals. To be round, you don't get a long enough straitaway, to be square, well, that wouldn't work out, much like rectangular, so, I guess the oval pattern was put to use because all the other shapes were either spoken for, or, too hard to work with. They tried just plain old strait, amd, well, that spawned a whole other sport. I guess it just worked out.