Companies and insecure individuals often insist their job titles should be spelt with upper case letters. We are talking here of narcissistic capitals.
This is incorrect grammar – capitals are used for proper nouns. Bus driver is not a proper noun. Nor is marketing director or chief executive officer. For that matter neither is president.
A job title can be a proper noun in some cases, that’s another issue.
People who insist writers spell job titles with capitals think it makes them look more important.
As if ‘head of marketing’ isn’t already impressive sounding.
Some people insist on using capitals even when they understand it is bad grammar. As my friend Chris Bell points out they worry that using titles correctly may show the world they are unduly modest.
So they deliberately show the world they are semi-illiterate rather than appear modest.