Back in the days when dinosaurs roamed the earth and photographers used totally mechanical cameras, it was common to have a camera serviced every few years. The springs in the shutter assembly had to be adjusted to keep shutter speeds accurate and various parts of the camera and lens could need lubrication. A CLA (clean, lubricate and adjust) was something that kept a camera in top condition.
Current cameras (and indeed most cameras made in the last few decades) really don't need a regular CLA. The shutters are electronically timed and in general no lubrication is required. Wiping off external dirt is about all the servicing that most film cameras ever needed. With digital SLRs the situation is slightly different since and dust or dirt on the sensor will be recorded in the same place on every image and despite automatic cleaning systems, you will eventually find dirt stuck to the sensor that shows up in your images.