Lolcows are best observed as the behaviors and personality of particular individuals, whereas Alt-Righters tend to guard their identities and move in crowds without distinct leadership. Making fun of an anonymous shitposter on /pol/ will be less rewarding than poking fun at CWC, for example, since one is ephemeral and the other is a known individual with a past, a present, and a future trajectory. High-profile Alt-Right targets tend to be difficult to milk for amusement, since either they have an air of professionalism that's difficult to break (like Jared Taylor or Richard Spencer) or they are willing to hit you back twice as hard (like Vox Day). I would also not discount the fact that there are probably plenty of people who sympathize with the Alt-Right, which would make them less likely to mock it.