When you say “benefit”, relative to what? If you compare it to a hypothetical scheme with no co-pay services, where everything falls under the a deductible reckoning, then it will be a substantial benefit for most healthy people.
Suppose you’re a healthy person. The only health service you turn out to need is 3 visits to your primary care physician, each for minor treatment. Co-pay is $25, but the total bill is $250 each time. You co-pay only $75 that year. Under a scheme where this service does not fall under a co-pay scheme, where the visits are treated as falling under the deductible reckoning, you would pay the full $750.
Sometimes co-pay is zero for certain treatments - often preventative treatments or routine health checks, even sometimes your first few regular doctor visits. It’s important to distinguish “co-pay = $0” from the absence of any co-pay scheme for a service. In the former case, you just pay nothing, in the latter case the service falls under the deductible reckoning.