Nelson,

There could be a few reasons. The most common is just neglect, I’ve seen banks and corporations lose properties simply for forgetting to pay taxes or HOAs, so letting a tax certificate expire isn’t that strange anymore.

A lot of certificates, especially in big metros like Miami, Tampa, and Orlando, are picked up by hedge funds (Capital One holds plenty). They often bid blindly at the minimum rate without even looking at the property. Later, when the redemption period runs out, they may realize pushing it to deed isn’t worth the trouble, so they just walk away.

You’ll also see this a lot in places like northwest Palm Beach or around Lake Okeechobee, where swampy or tiny parcels sit with expired certificates year after year because nobody really wants them.