That's not what they argued. The ECJ ruling is that the Uber is a company providing "‘a service in the field of transport’
within the meaning of EU law."
Uber claimed they weren't. They were claiming to be just an infrastructure service without any influence over the transportation part of the business. They wanted to do this since transportation services are subject to the local regulations as a specific exception to the normal Single Market rules on the provision of services (where you only required to follow your home regulations).
P.S. Your home regulations will include all the common European regulations but customer local regulations could be different.
Uber claimed they weren't. They were claiming to be just an infrastructure service without any influence over the transportation part of the business. They wanted to do this since transportation services are subject to the local regulations as a specific exception to the normal Single Market rules on the provision of services (where you only required to follow your home regulations).
P.S. Your home regulations will include all the common European regulations but customer local regulations could be different.