You're never prohibited from using AFCI or GFCI, you're just not necessarily required to it in all cases. The key requirement is that all receptacles in a bathroom be GFCI protected.
Relevant excerpts from Article 210:
(D) Bathrooms. In dwelling units, at least one receptacle outlet
shall be installed in bathrooms within 900 mm (3 ft) of t he outside
edge of each basin. The receptacle outlet shall be located on a
wall or partition that is adjacent to the basin or basin countertop,
located on the countertop, or installed on the side or face of the
basin cabinet. In no case shall the receptacle be located more
than 300 mm (12 in.) below the top of the basin. Receptacle
outlet assemblies listed for the application shall be permitted to
be installed in the countertop.
And in the handbook notes:
Section 210.11(C)(3) requires that receptacle outlets be supplied
from a 20-ampere branch circuit with no other outlets. However,
this circuit is permitted to supply the required receptacles in
more than one bathroom. If the circuit supplies the required
receptacle outlet in only one bathroom, it is also allowed to
supply lighting and an exhaust fan in that bathroom, provided
the lighting and fan load does not exceed that permitted by
210.23(A)(2).