There probably were random kidnappings.

But they only allowed Jews to live in ghetto’s in Nazi cities, so they knew exactly where to go. From there they were indiscriminate and retaliatory. But there was segregation before the mass deportation of Jews.

Also it was about the purity of the german blood and shit like that, so there were more allegations for people to be considered degenerate enough to be deported. Gays, gypsies, retardation, whatnot.