This is most likely because through childhood this is the type of thing they would have seen on "Scooby Doo" or other similar shows. Not to mention pranks from siblings that would simply throw on a sheet to scare you!
Ghosts can come in all shapes and sizes and so below I will describe the different "known" types of ghost. This can be used as a reference if you want to try and determine what may or may not being going bump in the night in your home!
The most general term for ghosts that we see. Generally apparitions are a "recognisable" ghost shape and don't appear to be solid (transparent).
Apparitions aren't necessarily just human form and may or may not appear to interact.
A cold spot is the description given to an area where a ghost is trying to manifest. Generally it's thought that in trying to manifest energy is drawn from the surrounding area. This creates a cold spot.
Cold spots can move around the surrounding area and paranormal investigators normally track this and use as evidence.
Another common type of ghost that is caught on camera.
Most orbs can usually be explained away as dust, water, insects or other floating objects but sometimes they can't be explained.
Orbs can sometimes appear on demand or appear to have other unexplainable features such as a face or emitting light that doesn't make sense.
Residual ghosts are like a recording of a past even that is playing on a loop.
Residual ghosts will never interact with you and instead will continue the same "loop".
An example of this would be a story my mum once shared with me.
She said she once saw a ghost hanging up washing. Or rather making the motion of hanging up washing.
Several people apparently witnessed this but the "woman" continues hanging up washing and didn't react to the people around her.
Eventually she faded away.
This one is fairly obvious. Interactive ghosts will interact with you! Simple!!
This can sometimes be confused with poltergeists, however poltergeists cause physical and emotional disturbances (we will cover this later).
Interactive ghosts will perform simple tasks, usually on demand.
An example would be to request a ghost to interact with an EMF detector. Sometimes the EMF detector will spike as the ghost interacts with it.
Poltergeists are probably the most heard of ghost. Mainly because this type of ghost was made famous by the Hollywood film by the same name.
Poltergeists are mischievous ghosts and cause a lot of physical disturbance such as throwing items or moving things from one place to another.
Poltergeists can also cause electrical disturbances and have even been reported to cause fires.
The least common of ghosts and can also be referred to as demons.
This type of ghost is the most unpleasant and are thought to have never been human (hence the name demon).
They can attach themselves to a building or person / family and cause great torment.
Entities show high levels of intelligence and thrive on negative emotions.
So there you have it. A short list of potential ghosts which will help you recognise the type you may be experiencing. Lets just hope you don't bump into the last one!