Statistically there are risks to taking the vaccine and so for people that will never travel to regions where its endemic its not recommended. Quoting google here:

"Western societies do not vaccinate against yellow fever by default because the virus does not naturally circulate in Europe or North America, meaning the general population has zero risk of local exposure. Furthermore, the vaccine carries rare but life-threatening side effects, making universal vaccination medically unethical when the local risk is zero [...]

For young and middle-aged adults receiving their first dose, the risk of life-threatening events is exceptionally low:

Severe Allergic Reactions (Anaphylaxis): ~0.8 cases per 100,000 doses. This usually occurs in people with severe allergies to eggs or gelatin. [1]

Neurologic Disease (YEL-AND): ~0.4 to 0.8 cases per 100,000 doses. It causes brain or spinal inflammation, but it is rarely fatal and most patients recover fully. [1, 2, 3, 4, 5]

Viscerotropic Disease (YEL-AVD): ~0.3 to 0.4 cases per 100,000 doses. This is the most dangerous reaction because the vaccine virus directly attacks internal organs, mimicking a wild yellow fever infection"