“Sold, Subject to Inspection”
Why would an agent show Buyers a home that’s already under contract?
Because the clients are (just) learning the market, and their agent is showing them the home for illustrative purposes only — that is, to educate the Buyer about how much/what kind of house can be had at a specific price range, in a particular neighborhood.
On Purpose vs. By Accident
Of course, the agent needs to first tell their client they’re doing that, and get their OK.
Otherwise, Buyers have a way of getting their heart set on a particular home — and understandably become perturbed (or worse) when they find out it’s already been spoken for.
Which in turn means that the listing agent (representing the Seller) must tell the Buyer’s agent once there’s a deal.
MLS rules explicitly require this — and levy a fine for non-compliance — but in a fast-moving market, it’s virtually guaranteed that some listing agents will be slow to communicate this crucial piece of info.
Other Caveats
Two other caveats apply to showing already-under-contract homes:
One. The home must have just come on the market.
Newly listed homes that sell immediately typically fetch full price if not higher.
Ergo, it’s possible to intelligently guess the sales price well before closing — the point of the whole exercise.
By contrast, homes that have been sitting on the market often accept a discount (“heads up” to would-be Sellers).
Two. The Purchase Agreement the Seller just signed has to allow showings until the home is past inspection.
Buried in the standard Inspection Contingency, this clause governs the Seller’s right to continue to show the home.
Most Buyers don’t object, because they’re in the driver’s seat during the inspection phase of the deal (if the Inspection is uneventful and they still want the house, all they have to do to seal the deal is remove their Contingency).
Leaving the Door Ajar
However, in a hot 2017 Twin Cities housing market littered with multiple offers, it’s at least possible that subsequent Buyers will 
want the house so much that they’ll write a backup offer so attractive that the Seller has an incentive not to address even legitimate inspection issues.
Then, there’s a chance the deal will falter, and another Buyer can step in.
To preclude that risk, Buyer #1 may negotiate for no further showings while they do their inspection.
When that’s the case, “just-learning-the-market” Buyers (and their agents) are out of luck . . .
P.S.: It’s also the case that some exhausted Sellers don’t want additional showings once they’ve accepted an offer.
See also, “Racing to Get Buyers Into a Home That Can’t be Bought.”
