The clock was crucial to timed recordings, which were how people recorded TV programs when they weren't around for them before things like TIVO existed. Set a it to record when your program's supposed to start and for X duration, put a blank tape in, go to work, come home and find it's recorded that daytime program you didn't want to miss.

If you weren't going to use that feature, yeah, it was pointless and could have just stayed blank rather than blinking 12:00 or whatever.