A design patent is available, but the bar for a design patent is very high and the income for most type designs is enough to maybe buy a nice dinner for two.¹ Copyright registration is easy and cheap.³
People who argue against type design copyright fall into at least one of three camps: (a) they have no idea what it takes to make a good typeface, (b) their ability to distinguish typefaces doesn't go much farther than distinguishing sans/serif/monospace (if even that), and/or (c) they hope to be able to use other people's designs for their own benefit.
1. Retail sales of typefaces is a ridiculously unprofitable business, which is part of why every nearly independent foundry/type reseller of measurable size is ending up under the umbrella of Monotype Imaging. The handful of designers who have made a living from type design either are employed as staff designers for Adobe/Microsoft/Monotype, do high-value custom designs for publishing clients (although these are becoming increasingly scarce as publishers who still do print are less willing to spend money on quality²) or, the big one but probably gone for good now, embedded fonts in printers (Arthur Baker's deal with HP, he claimed, left him set for life financially).
2. A big part of Font Bureau's early capital came from producing a custom version of Palatino for the gravure pages of Playboy that would match the printed output on the offset pages. There's probably a whole book to be written about the ways in which Hugh Hefner spent Playboy money in ways that nominally benefited the magazine but had a bigger impact in providing cash to artistic endeavors (most notably writers) that wouldn't otherwise see much money.
3. And optional. If registration occurs after an infringement, the copyright holder can only sue for actual damages. Pre-infringement registration also entitles the copyright holder to sue for punitive damages.