Do all men of a certain age need medication for help with their erections?

E.D. NOT universal. Erectile dysfunction (e.D.) is not universal but depends upon medical conditions. In some studies overall prevalence is 18% but rises to 50% of diabetics and 90% of men with combination of smoking, high blood pressure, and vascular (blood vessel) disease. Also prostate cancer surgery has high prevalence.
No. Trouble with erections (like erectile dysfunction) does not happen to all men. Age is certainly a factor, older men are more likely to have erectile dysfunction. Other factors that may cause sexual dysfunction are: meds (anti-depressants, some BP meds) , smoking, psychological, diabetes, and many others. Those who maintain overall health are less likely to have sexual dysfunction.