At first, let’s make it clear: font is not equal to typeface (type). Typeface is combination of qlyphs in one style or combined with one graphic idea. Font is actually a file (computer code) made to reproduce a typeface. So type is a drawing, font is a (computer) code to reproduce drawing.
So the right question is do we still need new typefaces and why?
The short answer is: —Yes, we do to express new ideas in our society.
To explain I need to go deeper in a typeface role in our society. Typefaces play sagnificent role in visual communications. Pictures are important eye-catchers, but main volume of information is still transferred through typography. Even in video format typography still important. The smartest analogy of typeface role belongs to Erik Schpikermann: typeface is a voice, that sunds in reader’s head. So do we need new voices for our messages?
Through the history of european/western civilisation every new idea in society brought new typefaces. The Renaissance brought italics instead of blackletter, and brought back Roman Capitals. Industrialization brought slab sefifs and sans serifs, and socialists suported Constructivism as main style of visual communications. It was because theese ideas needed to be presented in different style. Every time society finds a new idea—we need a different typeface to represent it.
Development of new typefaces is usually connected with «paper and print» technologies. New «paper and print» also influences typeface styles. So was with Didot: theese famous hairline serifs were impossible in time of Old-style serifed typefaces becaus of technology restrictions. Today we have less restrictions in typography and more posibilities than ever. And we, type designers, explore the unknown and experiment with typesace styles. Just because we can. And sometimes we feel certain new style will represent certain idea. Or some designer, using our typefaces feels it is suitable for certain communications. And that’s the answer:
We still need (and will be) new typefaces because of new ideas developed in our society. We can not predict the next big idea, we can not predict the next great typeface style. But we explore.