What is the most important factor that prevents us from applying educational technology?

I encountered this issue personally at PMU in Saudi Arabia.
When the teachers were presented with the new DynEd program they were very resistant to using it.
Reason: Fear it would dimish their authority or cause them to be replace.

Incomplete knowledge. A lack of process know-how and where to start on research and implementation initiaives is the bane of implementing anything new. 

Not available and applicable everywhere and both time consuming and expensive.

The lack of technology knowledge and technical equipment within the academic institution. Employing too old people that are not easy to teach new technology so that they can pass the knowledge to students. 

Personally, I was somewhat hesitant to implement things like smartboards into my classroom teaching because students generally have a lot of access to smart phones at home as it is, and I feel it is my job to engage with them in person. However, it is undeniable that implementing things like videos, internet research practice, and interactive software have significant postitive impacts on classroom learning, which is why I have embraced them wholeheartedly. 

Lack of training and financial limitations

Scarcity of educators who have developed their mastery and skills of using advanced technology due to the iceberg of fear lying in their depths.
I am a literature man but have studied programming back in1989 and I had graduated in literature back in1977.
Thus, what each educator has to do is to follow up the day to day advancement in technology and encourage others to do so.

Lack of technical knowledge and skill.