While someone might not entertain the thought of making an offer on a house already on contract, as the seller, I would inconvenience myself enough to open the door for showings.

The house isn't sold until closing.

I'd continue to keep an open mind about showings. However, traffic is going to drop to about zero once the property gets listed as under contract.

I don't think I'd have a problem actually doing the showing, however in my neck of the woods, the house comes off MLS when its in contract.

I guess it also depends on what normal contingency you are worried about and whats normal in your area.

For instance, in my area, no house goes in contract with an inspection contingency. Its dealt with before the contract or not at all. So pretty much all to be dealt with is financing and appraisal.