It's not actually a bed, it's a mattress cover. They are willing to sell you a mattress with it if you want, but the product itself is designed to go over your existing mattress. That said, good-quality beds cost money!
Well, you probably already have a bed, no? And if you don't, there are lots of different types of mattresses out there and you may have preferences.
As for frame, if you buy the Eight Sleep Pod 4 Ultra (which is the version that comes with a base that adds head/foot elevation control), you can use the base as a bedframe if you like, though that would be pretty minimalistic.
If this product was an entire bed then it would actually be a lot less appealing because it means you have to replace your bed to use it. It's not a bed, it's a mattress cover (and optional base with the Ultra), so it's purely additive on top of your existing bed, and does not significantly alter the feel of your mattress (besides temperature).
