Helvetica is the Ikea of fonts. It has its place; selectively. It sends a strong message. Its safe, its generic, its proven acceptable design, its corporate. But unless thats the message being conveyed in a scene; thats not what filmmaking is about. Avoid it like you avoid Comic Sans.
Fonts are important. If any of you have ever gone font hunting online, especially when trying to find 'that font', you know the thick forest of font I speak of.
Fonts can give away your period set in an instant. Likewise they can give away fake road signs. They can make a piece of artwork or graphic look amateur or professional. Sometimes we don't realise it; sometimes it just comes across as odd. Or bad design. Fonts are a look. The look is of an era. They need to belong. Sometimes they need to be recreated; sometimes you can closely fake them.
There's alot of free fonts out there. Be sure to check they are royalty-free/public domain if you are using them on a production.
Its really important to research the fonts you will be using for your project. Its easy to be fooled by an old-looking font if you aren't well rehearsed in font theory.
Its one of those "little things".