I've recently listed an occupied home where they ask for two hours notice so the home can be ready and the large dog secured.  I've had agents make appointments and never show up!  BUYER'S AGENTS:  This is the ULTIMATE in RUDENESS & DISRESPECT toward the seller.  If you make an appointment and find you cannot make it for one reason or another, call the listing agent and let them know!  Don't leave the seller outside in near 100 degree weather walking a dog around for an hour waiting for you to come and go - put yourself in the seller's shoes and have some compassion!  Yes, they want to sell their home and are accommodating your showing - have enough respect to show up or call to cancel if you cannot make it!