Good example, at least historical. ;-) I wonder why they never added single line comments before. I mean it took them quite a long time to do so. Languages before 1960 even had single lines too.

Edit: BTW it was common in C to write multiline comments to have them look like single line comments too, because that's easier to read and understand. Maybe that's why they didn't feel the need for, because in practical usage it could be replicated. In example as:

/* Title
 * description
 * variables
 */

This could easily be replaced by single lines as:

// Title
// description
// variables