Some of my favorite female vocalists (pop or otherwise) include the likes of KT Tunstall, Michelle Branch, Sarah McLachlan, Dido, Lisa Loeb, The Indigo Girls, Liz Phair, Chrissy Hynde etc.
There are some very fine "pipes" in that group...McLachlan especially, but (sticking with Sarah as an example) she's often hindered by the fact that her material is more often than not, medicore. OTOH, KT Tunstall's material has been very good to great overall, but she has a voice that probably couldn't be considered as great.....but it has a certain smokey sexiness to it like that of a Chrissy Hynde which I find much more charming and warm than someone with operetic range.
In any event, I still feel that having pipes is non-essential. I'll bring up Pat Benatar again as an example. Incredible range and all that...but her records were terrible. What good is having a great voice when the material it's applied to is basically unlistenable?