I think "need" is related in general but individual circumstances also play in. A psychic working with police has little need but has innate talent that can be applied regardless of individual need. Most people have no 'need' and even in many cases, it is detrimental to the psyche (distracts from the here & now) so the ability is greatly diminished for them.
I think "need" and purposely "sought out" both are both important parts of why one may be able to RV. There is also one more reason and that is that "someone", call it Guardian Angel/Spirit Guide of "other", is looking out for you. But I think we are using term RV wrong here. At least from the way it was designed to be used, as in using specific coordinates to see what is there.
We should call this a sense of "knowing". Knowing can envelop knowing of a person upon just meeting them. Meaning being able to read their story immediately as you shake their hand or they get into your energy space.
Then we have the knowing a physic has when aiding the Police, through intent. I tried this a couple of years ago when someone made a thread asking why don't we don't help police, gov't, etc., if Astral projection was real. He basically came here to challenge us, as often occurs on a Forum of this nature.
That night I did indeed try to see something and what I saw I couldn't stomach. "Knowing" for the Police wasn't for me. I did actually see the area that they found the guy. But I also saw very graphically how he had murdered his victims.

That was still intent though. This a link to that thread:
http://www.astralpulse.com/forums/welcome_to_psychic_and_paranormal/why_are_psychics_not_used_by_police_to_find_missing_persons-t39765.0.html Then comes the "knowing" I received by a Guardian Angel/Spirit Guide that actually saved MJ and I from a very stressful and bad economic situation.
This is a post I made here from back in Nov 15/2013 after this question by another skeptic here new to the Astral Pulse Forum.
"You say 99.9% of all validations happen unexpectedly, I ask me really why! why u cannot control it if its real possible to get new information in OBE. You would have such a big advantage."
My response:
"I have one for you Ofen! smiley
Two years ago MJ and I were to have a store in our local Mall. We paid the contract for the store and were set to open it in 30 days. I did a Phase session and saw that I was in the Mall, but working at a Kiosk, not a store and that I was selling 2 completely different products, that we had never sold before. Actually they were 2 products that I didn't know anything about. We had our own inventory ready to go as it was and had no need for these other 2 things.
Trusting my vision, I searched everywhere and set up a line of distribution with the needed companies. I told MJ of my vision. She didn't want to hear any of that talk. A store gave her an area to paint and sculpt her beautiful Dragons. It gave us a bathroom, a sink, a door, etc. In the past we had sold on Kiosks, but for the previous 4 years we had a temporary store location. I finally talked MJ into ordering a "small" amount" of these two new things, one being a Salt Lamp, the other a Glass Blown Jellyfish. I upped the order though, unbeknownst to her.
Two days before we were set to go in the Mall, MJ phoned them for our key. About 5 minutes later we received a call saying they had made a terrible mistake. Our store was in Michigan, not Minnesota. Michigan is a looooooooooooong way away from Minnesota. This hit MJ like a knife in the heart. She had spent the last month and half sculpting Dragons and preparing for our store. The only option the Mall office had was to give us a Kiosk and so my Astral vision came true.
That year we sold Salt Lamps on one side and Glass Jellyfish on the other. Had I not of seen it in my vision we would have taken a major financial loss. We can't sell her Dragons on a Kiosk. There is no where for her to sculpt or paint them there. A Kiosk is a small booth in the aisle of a Mall that is approximately 7 ft wide by 10 ft long. Our store was to be about 60 square feet."
So yes, "knowing" can go both ways, intending to know or a need to know basis. I guess the same could be where I get a weird vibration or tingle upon meeting someone or something that I shouldn't get to know any better. I always though that my "Spider Sense" is tingling, lol.
That "Spider Sense" made itself well known back in my youth. I remember one instance I was waling into a Home where a great party was being thrown. I had a case of beer on my shoulder and a big smile on my face. That is until I entered the Home's threshold. As soon as my foot hit the bottom of the doorway or the entrance to the home, I got a electric shock. It was like a bot of lightning hit me. I stepped back for a moment to collect myself, then proceeded forward again. Bam, it hit again. So I turned to my friend, handed him the case of beer and left.
That night the party got busted by the Police and many underage tickets were given out. So, someone was looking over me that day.