I do both, depending upon the arrow's final look.
Plastic nocks take me probably less than a minute from tapering the shaft to gluing on the nock.
A horn-reinforced self-nock takes me maybe an hour total per arrow, possibly a little longer.
Not everyone wants a self-nock on their arrows. they're difficult to fit perfectly to the string, they can't be color coordinated, and they take a lot more time.
Of course, the coolness factor does have to be considered.
Make the choice and do what you want.
Also, be careful about assigning "traditional" value to things. That's a very, very slippery road. Some archers may think to be traditional you have to make your own bow with stone tools, others are happy with using carbon arrows and calling themselves traditional archers.
There's room for everyone without trying to say one person or piece of gear is more traditional than another.
Guy