Open houses are a bit of an enigma. Let's consider 3 key factors:
1) If you do the quick research, you'll find that only 1% to 2% of homes are sold because the buyer came to the open house, liked it, and decided to buy it. That's a dismally small percentage.
2) On the other hand, in a survey conducted by NAR, fully 45% of home buyers surveyed said that an Open House was a source of information used in their search for a home.
3) Agents primarily conduct open houses to meet buyers and to keep sellers happy. Once the listing contract is signed, there isn't much a seller gets to "see" the agent doing to get the home sold. Holding an open house is the most "visual" thing an agent can do to convey to the seller that they are working to get the home sold. So agents will do them to please sellers. Especially the ones who are overpriced.
So let's summarize. Let's say that you were told to go to work every weekend for TWO YEARS (in addition to working all your normal hours through the week) but that you'd not get paid to do so except for ONE of those 100 weekends. Would you do it? Probably not. Agents do open houses to meet buyers primarily.
Buyers DO use the open house as a source of info that factors into their buying decision but since they don't typically buy the actual home being held open, they are using that information to help them buy a DIFFERENT house!
Why would you want to get kicked out of your own home for a weekend afternoon, have unqualified people tramping through your home, and even the "real" buyers only using your home as a source of comparison for the home they that eventually WILL buy?