Sure, it's a legitimate question: Can you sell your home without the representation of a professional real estate agent? The legitimate answer is, Of course you can - but that begs the next question of whether it makes sense to do so.
One assumes that sellers want to obtain the highest price possible. Otherwise, the home could simply be auctioned, or sold to the first buyer who offers. Getting the best price depends upon exposure to the widest, most qualified segment of potential buyers.
An ad and a yard sign are not enough to create that exposure. While agents spend untold dollars on advertising and signage, those only attract about 20% of actual buyers, so just one ad and one yard sign will yield even less.
So where does the lion's share of motivated buyers come from? In a real estate firm, they come from cooperating brokers and agents. It's logical, since serious buyers seek the assistance of agents who save them time and money by matching their needs against large inventories.
The only buyers attracted to properties “For Sale By Owner” are ones who want to save the same commission that the sellers do! You can choose to represent yourself in this competitive industry, but it may cost you. Remember that a bargain is not measured by what you pay, but by what you get.