Hi everyone,
I've been browsing various pre-flop raise-first-in (RFI) charts and I've noticed that in most charts the Button raises a larger percentage of hands when folded to than the small blind. The button might play something like 40% of hands whereas the small blind will only play around 30% when folded to.
I'm confused as to why this is? The sb is getting a better price than the button (when folded to) and only needs his raise to get past 1 other player (vs. two players from the BTN). The only reason that I can think of is that the sb would be out of position post-flop, but does that really justify playing around 10% fewer hands than the button?
Any insight would be appreciated thanks!

position is pretty important. the button also can win more, 1.5 bb vs just 1 bb for a successful steal attempt, and while the BB will be quite inclined to defend against the SB getting 2:1 and being in position, the blinds will be less inclined to defend against a button raise because they are out of position.

At low stakes, you can "exploitatively" open a fair bit wider in SB, as villains don't defend often enough. i.e. Most of your EV comes from pre-flop steals, and you only have to get the raise past one player.
Against tougher players that call or 3-bet more, I think the SB opening frequency should be a little bit lower (and limping some hands may be appropriate), because the positional disadvantage is more of a factor when you're playing against strong players. i.e. They won't fold to the raise pre very often, and they will use their positional advantage post-flop to make your life miserable.
Generally speaking, I think that until you're playing 25NL+, you can probably open more or less the same hands in both positions (BTN and SB), but whether your opening frequency is 30%, 40% or 60% should depend largely on who is in the BB. (Steal more often vs nits, don't steal so often vs loose players).