Order is a sequential pattern.  The start is labeled 'first', the next thing is labeled 'second', and so on.  In literate societies the words or sounds for the alphabet are one of the first patterns taught to children using order.  Typically a mnemonic device, often a song, is used to facilitate learning the sound of each letter. Perhaps it is the sequential-ness of teaching the alphabet that triggers parents to teach numbers by counting.  Regardless, the correlation between first and one, second and two, third and three, and so on is extremely difficult for a child to discriminate between when the symbols used for both are nearly identical.  First usually has a period or parenthesis after the one: 1. or 1).

Another consequence of using the concept of order when teaching numbers is that order is the foundational concept of process:  perform step one, perform step to, etc..  This takes mental effort to memorize the steps, not unlike the mental effort, and painful memories for some, to learn the alphabet. Learning numbers by counting, subjects the child to a painful memorization process which erroneously lays the foundation that learning anything to do with numbers can be painful.