The main reason is NEC doesn't mandate them for 240v setups. 210.12 says (2014 rev quoted, emphasis mine)
210.12 Arc-Fault Circuit-Interrupter Protection. Arc-fault circuit-interrupter protection shall be provided as required in 210.12(A) (B), and (C). The arc-fault circuit interrupter shall be installed in a readily accessible location.
(A) Dwelling Units. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, or similar rooms or areas shall be protected by any of the means described in 210.12(A)(1) through (6).
Now, you can find 240v breakers with CAFCI protection. They're pricey, but they are out there. The same can be said for 240v GFCI breakers. The reason there's no dual function breakers likely has to do with them probably costing a great deal by themselves. I mean, a 240v 15A CAFCI is over $100 by itself.
Then there's the need for a GFCI on a 240v line. A subpanel doesn't need one. A dryer or stove doesn't need one. An EV charger will likely have it's own surge protection, which should cover the GFCI portion. There's just not a lot of call for 240v GFCI, and if you do need one, there's no mandate it be AFCI as well.