Are there land-based Bitcoin slot machines?

Yes, as of 2018 there is one terrestrial establishment offering BTC slots and gambling – the Merit Hotel Nicosia in Cyprus, and there are also machines called SmartBoxes for BTC for gambling games that are in their beta phase of testing, but for the most part, you’d usually head over to an online casino to play BTC slots. The reason there are few land-based slots is because of jurisdictional limitations and regulations on the use of BTC and other cryptos, but who knows, perhaps land-based slots won’t just be for show, and they will become quite popular in the future.