The medieval/early modern ones were plenty damn lazy, given that “not working for a living” was pretty much the definition of their social identity and actually doing a day’s work would be acting like a serf.
However, I would say the main difference is that the medieval/early modern nobility had two things that occupied a good deal of their time:
- estate management: even though most of the “shop floor” work was done by stewards and bailiffs and the like, the lords did spend a lot of time on the management side of land management.
- a monopoly on political power: in the premodern era, pretty much all jobs in politics were held by nobles or nobles who had joined the clergy; there were seats in Parliaments or Diets or Estates, there were places at court or in royal government/administration, there were judicial positions, there was the aristocratic domination of the army, etc.
After the economic/social/cultural/political transformations of the 17th-20th centuries that could collectively be described as “modernity,” the nobility lost those “places” in society. On the land side, they either lost a lot of their land or shifted their money into more liquid capital (which meant they could move to the city) or gave into the need for fully professional management (ditto, with a side of absentee landlordism). On the politics side, the rise of mass democracies, professionalized civil services, and militaries, abetted in no small part by the fact that the aristocracy had enthusiastically blundered their way into tons of increasingly bloody wars meant that noble titles shifted from a necessity to a liability.
What was left was their traditional pursuit of the “gentle life.”