Digital cables: 75 or 110 ohms?

What are the applications in using a 75 ohms digital or a 110 ohms? I have seen that most RCA to RCA digital cables are 75 ohms and XLR to XLR are 110 ohms. Are they all made that way?

Thanks to all of you for your help,

They should be. That is how the S/PDIF (coax) and AES/EBU interfaces are specified. The balanced cables are more RF-noise-immune and carry higher signal levels. There are other differences in the data protocol but, overall, they are similar. I generally use the balanced if possible.
The SP/DIF spec is 75 ohms, single-ended signalling. The AES/EBU spec is 100ohms balanced or differential signalling.
AES/EBU spec is 110 ohms, not 100.