It occurred to me that Martijn van Buul wrote in gmane.os.netbsd.help:
> It occurred to me that David Laight wrote in gmane.os.netbsd.help:
>> Try adding another file that contains:
>>
>> # REQUIRE: cupsd
>> # BEFORE: samba
>
> That would've worked, but samba doesn't PROVIDE: anything. Maybe it should.

But smbd does. Silly me. Solved.