I think there are multiple reasons why Anakin's force ghost did not appear to Kylo Ren throughout The Force Awakens:
1. Disney wanted to reboot the franchise and did not want to mention anything from the prequels
This does not mean that the prequels aren't canon--they are. But Disney did not want to mention them due to them being hated by the majority of the Star Wars fandom. Several materials teasing a romance between Shmi Skywalker and Qui-Gon Jinn as well as the mention of midi-clorians were scraped due to Disney not wanting to upset fans. This is probably why any concepts involving Anakin Skywalker's ghost was eventually given up on. And if followed, Hayden Christensen would have had to reprise his role as Anakin which probably would have been refused by the actor who received backlash for his acting in the prequels.
2. Kylo Ren idolizes Darth Vader
Kylo Ren views Anakin as being weak and foolish, he would not listen to his ghost even if he appeared. Han Solo stepped into the role of advisor, rather than Anakin, to try to speak to Ren's conscience. Kylo Ren talks to Vader, not Anakin. Vader could not appear before Kylo since he was killed by Anakin upon saving his son. If Kylo killed Han after his pleas to come home, it is safe to assume that he would have paid no heed to his grandfather's ghost.
3. It does take effort to appear as a Force ghost
This is addressed in the canon Star Wars book, Beware the Power of the Dark Side! (by Tom Angleberger):
Like most Jedi, Obi-Wan became part of the Force when he died. But Obi-Wan did something the others did not. Guided by the discoveries of his own master, Qui-Gon Jinn, Kenobi found a way to live after death and even return to walk briefly among the living. Not for himself, not for some greedy dream of immortality, but to continue the great fight against evil and tryanny. It takes great effort, a great will, but he collects himself, pulls together the pieces of his consciousness from the endless flowing energy of the Force, and appears before Luke. He cannot do this often, only at key moments in Luke's journey, when a misstep might spell doom, not only for Luke, but for any hope of bringing balance back to the Force and freedom to the people of the galaxy.
Obi-Wan can sense his strength growing weak. He cannot bend the laws of nature any further. He must go.
4. Han Solo said everything that could be said to Kylo
As I said before, Han Solo stepped into the role of advisor and in place of Anakin's force ghost. If Anakin's ghost appeared, there would not be as much of an emotional stake as we have not had any interaction with the two of them. By keeping Anakin out of the way, there is more of an emotional tie to the character to know how he would view his grandson's actions. But it also creates an emotional bond to the character of Han Solo, his development as a character, and his relationship with his son. Han said everything that needed to be said: how much Ren was still loved by his parents, they were willing to forgive, Snoke's true intentions, and that there was still good in him. It reminds the audience of Han's heart of gold, raises the stakes, and will form Kylo Ren's path to the light or the darkness.
It also bonds the audience to Anakin Skywalker, not Darth Vader, to know how the character would view his grandson's actions.