But usually such homes aren't significantly overpriced. Just a bit to provide that wiggle room.
Every situation is different. But the way it often works is this: A listing agent will look at the comps and determine at about what price the home ls likely to sell. Let's say, based on comps, the agent thinks the home will sell for $300,000. The agent presents this information to the seller.
Now the seller has a choice. Does he want a quick sale and price it at $280,000? Does he want or need a bit more money and price it at $299,000? Does he want to build in ample wiggle room (price negotiations, seller subsidy, etc.) and still attempt to maximize his net and price it at $329,000? Or does he get greedy (or look at other houses on the market, not the ones that have sold) and price it at $349,000?
All of those scenarios happen all the time. In all but the last (clearly overpriced), the listing agent probably will be fine with the seller's decision. If it's really overpriced, though, some agents won't take the listing. Others will, but will discuss with the seller the need to reduce the price if there are no offers within, say, 30 days. And there are a few agents out there who will tell the seller that the house is really worth $349,000 . . . often just to get the listing.
Understand, too, that in today's market some people owe so much on their mortgage that they can't afford to ask (and accept) what the property is really worth. Unfortunately, it means they won't get any offers. But in the scenario above, let's say the house is worth $300,000 and the seller owes $310,000. In that case, the seller can't sell for less than about $340,000 without bringing money to closing. So the seller may put the house on the market for $349,000 and then reduce it to $339,000 . . . but then go no lower.
But to answer your question about whether there's an expectation that buyers will automatically offer less than the listing price--often, yes. Buyers also understand that lots of sellers will ask for closing costs. So it's not unusual for sellers to ask for 5%-7% or so more than they expect to end up with. That's not always strategically the best move, but it does happen.
However, a buyer really should pretty much ignore the listing price. A buyer should determine what the house really, truly is worth. Then pay no more than that. Perhaps offer less. A Realtor can help with that strategy.
Hope that helps.