Why is the first partition on a device called 1 and not 0?

Just curious  why the first partition on disk is 1 and not 0, as computers count from 0 up
ex /dev/sda1 on my computer. shouldn’t it be /dev/sda0? or is /dev/sda0 implied as the disk itself?

Max number of partitions is 15 for SCSI and all the drives using the new SATA driver, 63 for IDE drives (0 is the full drive, 0 to 15 is four bits 0 to 64, 6 bits)
/dev/sda0 would be the full drive, and 1-4 would be primary partitions. As to why they don’t use /dev/sda0 instead of /dev/sda, probably because the number indicates a partition, and not a full device.