@ᴜɴᴡɪʟʟɪɴɢʟʏ made a post on the same concept about two weeks ago (change your name I can't @ you wtf)
I'll offer my thoughts:
Fear RP is hard. Be it because it requires proper roleplay from both sides - Well written emotes to keep the general vibe going - or be it because roleplaying fear is allowing your character to be perceptible to whatever is happening to them.
Part of this is the mentality where people try to win in a situation, rather than collaboratively tell a story. I'm personally of the opinion that there's no such thing as winning or losing in roleplay, and that there's only moving the narrative forward. Regardless, people's opinions on this matter differ wildly.
In addition, there's a thing about consequences. Let's say your character is getting attacked - and you're roleplaying with a person you don't know at all at this point - and you're almost certain they are going to get killed. Unless you PK on first CRP death, there will not be any real consequences for you or your character, which causes people to lose interest in the roleplay.
On the other hand, let's say you do PK on your character's first death. Now you do have consequences. However, if you get too attached to your character, you might opt against roleplaying this fear. Because, as mentioned above, it removes some control over this character - ultimately putting them in danger of being PKed.
Similarly, if your character does not get killed, but finds themselves in a situation where fear RP would fit, you still face the same problems. There would likely be consequences to this roleplay - And are you, as a player, ready to take these consequences?
TL;DR
A lot of this comes down to how we, as a community, look at the characters we play and the value of roleplay - Regardless of whether it has consequences for our own characters. In addition, fear is a damn hard emotion to roleplay and asks a lot of good roleplay from both sides.