I think many members of the Church would agree that sharing the gospel is difficult; or rather sharing it in the manner the full-time missionaries want them to. Why is it difficult?
I think a large reason is that it is so artificial. We pick someone we know (of) and set a date by which time we will have shared the gospel with or invited them to church or whatever. The problem is that method is so transparent. The average person can see through false motives, especially in places in Utah and southern Alberta where they are familiar with the motives of Mormons.
Full-time missionaries seem to be convinced that simply opening our mouths (even to the grocery store clerk or the gas station attendant) is the best way to bring in the converts. They seem to be convinced that when members share the gospel how they share it does not seem to be as important as the fact that it is the members sharing it. They have this idea that as long as it is the members doing it, it will have this magical effect on people.
Unfortunately, it does not work that way. People need to know that you are befriending them because you sincerely like them and not because you have set a date with the missionaries. A friendship needs to continue and flourish despite whether or not the friends ever accept the gospel, and if they do, the friendship needs to go beyond the date of baptism.
It is easy for missionaries to talk about the gospel with everyone they meet. Everyone they meet expects it of them. Missionaries are artificial. They dress artificially, they live artificial lives, they try to build artificial relationships, everything about them is artificial.
Which is why when so many get home and become natural again, they have difficulty sharing the gospel as they did on their missions. The artificial uniform is gone, the artificial life is gone yet they are still using artificial methods to share the gospel.
The gospel is all about love. Showing love for others. Developing a Christ-like love. Nourishing an unconditional love. When people know we love them, they want to be close to us; they want to be with us. That is how the gospel is shared. More neighbours will be converted because of a Mormon who shovelled their walks. More coworkers will be converted because of Mormons who offer compliments each day. More friends will be converted because of Mormons who support them, strengthen them and encourage them.
It is less about telling someone about Jesus and more about showing someone what Jesus did.