Do men need to take testosterone?

Sometimes. Testosterone decreases1.5-1.8% every year after age 40. It's not just about sex and sex drive! Testosterone is important in many areas including bone health, energy level, Insulin resistance and depression among many other areas. There have been studies linking low testosterone with increased risk of all cause mortality.
Sometimes. Testosterone is a male hormone (also found in low amounts in women) that can diminish with age. Low testosterone can result in loss of libido, impotence, weight gain, etc. Fortunately, testosterone can be supplemented with prescription testosterone (gels and injections) to help raise the testosterone to more normal levels. See your doctor if you suspect low testosterone for a simple blood test.
Mostly no. Most men do not have an issue with their testosterone levels. There are many men that do need to take it depending on their personal issues. An example would be a person who had to have their testes removed because of a disease. Please consult your family physician to see if you need a supplement of testosterone or not.