There's a fundamental difference between the pioneer and the explorer.
The explorer, very often, is well to to do, comfortable, he benefits from his position in society. He goes exploring because he's restless and bored, too comfortable, and because he can afford it. He's basically an adventurer, a playboy, maybe an entrepreneur. He's the Conquistadude.
The pioneer travels into the wilderness because he has little choice. He's at the end of his tether at home, he's desperate, he's ready to take any risk, even the unknown, rather than endure his dead-end position in the old country. He's the indentured servant.
The question of space is which of these two opposing groups is most likely to want to go--or to be able to go.