The demand for toddlers might be lower than supply, but the whole market of older children is a small fraction of the overall adoption market, which is a small fraction of the overall child market. Each year, only about 20,000 kids age out of foster care without being adopted, versus about 70-80,000 babies who get adopted, versus about 4,000,000+ births.

In any case, adopting an older child is a huge undertaking and not something someone should do just because she wants a child. These kids often already manifest issues resulting from parents who are drug users, etc. They need much more support than your typical child.