The short answer
They provide context on price movements, previous buyer demand, and whether properties have experienced difficulty selling.
If a property has changed hands recently, or sat on the market for a long time before, that history is useful leverage in a negotiation. It tells you something about demand that the current asking price alone won't.
Why this matters for your purchase
This is the kind of thing a PropM8 Property Intelligence Report is built to surface early, before solicitors, surveyors or lenders are involved, while it still costs nothing to walk away.