To be eligible to be registered as a trademark, a mark has to meet two basic criteria: be distinctive enough (either on objective merits or by gaining distinctiveness through extensive use and recognition in the market) and not conflict with other already registered trademarks.
Let's look at why a unique font doesn't influence a word mark's distinctiveness:
A word mark is a type of trademark that protects only the textual elements of the mark. When it comes to a word mark's distinctiveness, you can think about it this way - if consumers were to write your brand name or say it out loud, would it be inherently distinctive? Would it clearly protect you as the source of given goods and services and prevent confusion in the marketplace?
Therefore, a unique font is merely a stylistic element that in itself does not provide distinctiveness to a word mark.