We allow all sorts of encumbrances to transfer with property. You can sell a house with an easement that lets neighbors use some amount of your property for access, with a tenant who has a contractual right to stay to the end of a lease regardless of what the new owner wants, or with a covenant to limit development. Hell, a couple years back an entire mall sold for $20 with the agreement that the buyer was assuming all of the seller's debt and also the seller's contractual obligation to perform road maintenance. If you couldn't transfer these agreements with a sale they'd be useless even absent a sale. Either no one would buy the property because its unsellable and the value would plummet or you would buy it with the encumbrances, transfer ownership from your left hand to your right hand to remove them and then do what you want.