How might measuring service quality be more difficult than measuring product quality?

Now a days quality of a service and Product can be measured easily but when they compared certainly product quality in terms of its life, functionality, durability, Price, Value and satisfaction can be measured using analytical tools but in case of service you have to rely on the consumer responses against price, value, satisfaction etc. 

Products are tangible; therefore, measuring quality across several dimensions such as durability, functionality, and so onmay be easier or performed more consistently than when measuring service quality.