Implied warranty of habitability bases rights and duties on status
One way to look at an implied warranty of habitability is that it bases rights and duties on status, rather than contract, which harkens back to Feudalism when status was the usual source of rights and duties.
Cornelius J. Moynihan & Sheldon F. Kurtz, Introduction to the Law of Real Property 2 (4th ed. 2005) (emphasis added):
The relationship [of lord and vassal] was usually evidenced by the solemn ceremony of homage where the vassal knelt before the lord, acknowledged himself to be his lord’s man and swore fealty to him. It was frequently accompanied by a grant of land from the lord to the vassal, the land to be held of the lord by the vassal as tenant.(1) Normally, by the terms of the grant specific services were imposed on the tenant and these services were considered to be a burden on land itself.
(fn1) Land was not the only subject matter of a feudal grant. It was customary throughout Western Europe in the Middle Ages for great and petty lords to obtain vassals bound to render military service by granting to such vassals a monetary annuity. The feudal bond was created by the rendition of homage by the grantee to the grantor. These grants numbered in the thousands. See Lyon, From Fief to Indenture (1957).
In the medieval period status, not contract, was the usual basis of rights and duties. It is interesting to observe that by the twentieth century there had been some retreat from contract back to status as the source of rights and obligations. See, e.g., Javins v. First National Realty Corp., 428 F.2d 1071 (D.C.Cir. 1970), cert. denied, 400 U.S. 925, 91 S.Ct. 186, 27 L.Ed.2d 185 (1970) (landlord held impliedly to warrant the habitability of rental housing units).