Much depends on the personal financial circumstances of car owners. The question is always whether they could afford to foot the bill for possible repairs running to several thousand francs, or even a total loss of the vehicle, out of their own pocket at all times.
Fully comprehensive insurance is generally required for vehicles pre-financed via leasing or other forms of credit. Fully comprehensive cover is certainly also worth having for nearly new vehicles. However, from a risk point of view it can also make sense to take out fully comprehensive cover even for older vehicles, depending on the vehicle's residual value.
It's definitely always advisable to take out partially comprehensive cover as this covers risks such as fire, high water, floods, hail, theft, glass breakage or damage arising from collisions with animals, which would otherwise not be insured. The premium for a partially comprehensive policy is very reasonable when compared to the potential cost of damage caused by such incidents.
Whether it's still worth taking out collision insurance even for a second-hand car depends on the vehicle's current value and also on whether you could afford to pay for any possible damage out of your own pocket. Even a second-hand vehicle could well still be worth several thousand francs and provide several more years of service.