PIE voiceless aspirates

Is there a necessity to reconstruct voiceless aspirates (i.e. ph th
kh) for the Indo-European proto-language?

Many books I've come across does not postulate them for PIE. On the
contrary, my own teacher of IE Comparative Linguistics (W. Smoczynski)
argues that their presence is necessary in order for the system to be
phonologically complete (i.e. to have the opposition between the
voiced and voiceless aspirates). Can someone tell me what's the
general opinion on that subject?

I'd be grateful for any help.

Dariusz