There are paintings that are meant to be viewed in galleries, but they are relatively recent. Historically, most paintings were commissioned by individuals and institutions...i.e. the were painted for patrons. There's about three centuries between painting the Mona Lisa and the opening of the Louvre. Or to put it another way, Renaissance paintings in an art museum are somewhat analogous to 2001 on an iPad and a person could make an argument [1] that part of what makes modern art modern is that it is painted for a world in which art gets displayed in museums.

[1]: I'm not making that argument. The argument I am making is that a person can make that argument.