Houses Are Listed That Owner Is Not Interested In Selling?

[MDWCT2018]

Been speculatively looking online at listed properties for sale.
One of the most bizarre things I have noticed is that many properties are listed and are open, but on further enquiries turns out that the owners are not interested in selling. However they still remain actively online and I don't understand why the estate agents don't then take it down?
It is happened enough times for me to wonder why this is? From a buyers perspective it's obviously a waste of our time looking at listed properties that the owners have no intention of selling. Is it done for remortgaging purposes or loans et cetera. Could somebody please shed some light on this? Thanks

[barry1010]

I think estate agents prefer to keep them listed as it makes them look busy and popular to attract new sellers