We do.
It is not the prime reason. The prime reason is the world view held by militants whereby the view all military operations as being conducted on the "behest of the US". They view the state's involvement in the WoT, including the Operations in Wana, Tirah, Orakzai, Mohmand, Bajaur, South Warizistan and Swat as only for "pleasing the US". The drone attacks are an additional factor but in no way the prime factor. The world view of West-is-out-there-to-destroy-Islam and these-are-West-stooges are the main reasons. The toxic religious dogmas of declaring everybody not cooperating with you as Kafir and liable to death is a major factor.
I'm too sick of this drone attack = suicide bombing BS. I can't take more of this as this has no grounds. Yes, they can be used as a motivating factor, but there is no, absolutely no evidence whatsoever that any suicide bomber has been linked or a potential bomber that has been apprehended had any acquaintance that died in a drone attack. Bring forward any news report, intelligence report or a case report that states that the person caught or who carried out the bombing had any relative that died in a drone attack and he was avenging his family members. All the time people start making this assumption without any evidence.