If you have the right soil and plenty of safe ground water there is nothing wrong with septic and wells in the suburbs. However even at suburb density public systems are not that much more expensive and you gain never having to worry. I have several times in my life on well water turned the faucet on and no water - $2000 to a well driller to replace the pump and I had water again - the pumps last 30 years though essentially no other costs (electric but that is cheap) so overall a well is cheaper. With a septic system it is $600 to pump it every few years, but if the system fails it is $30,000 to replace it.

Again though this depends on where you live. In some places filter raw sewage through 2 cm of dirt and it is safe to drink - in other places raw sewage will travel miles. Likewise some places have plenty of safe water, other places have little water and still other places the water isn't safe to drink.