-- Builders are not building the kind of properties that buyers want. In my market these are suburban tract housing generally at a sub-$500K price point with low-end construction materials and finishes. Thus, buyers say "there's nothing to buy" because they aren't the kind of houses they want. They end up buying them anyway because it's all they can afford and/or other factors like proximity to work or family. But, looking at days on market, etc, relative to other properties, it's pretty clear buyers of these homes are acting more out of desperation.
-- Obsolescence. We have a lot of (older) houses in our area that are simply not conducive to modern living and until someone is able to do major overhauls, they will always be less desirable. Think tiny parlor rooms, bedrooms that barely fit a double bed, kitchens closed off from the rest of the house, single bathrooms, etc.
-- Non-turn key properties. My market is such that many local buyers live paycheck to paycheck and will not be able to afford renovations of any kind. Thus, the people buying non-turnkey properties are our out of area newcomers (of which there are many) but these buyers are such that they tend to want more amenities than our existing housing stock can provide. So basically anything not turnkey is sitting longer even in a competitive market.
So my point in all of the above is to say that in some markets, I believe there is more inventory than believed, but because it is not in line with market expectations you end up with the general public believing there are limited opportunities.