Some LEL questions about 3v3 pocket/ flank Meta

Hello people,

I know the meta is that the pocket player in a 3v3 plays a cav civ and the flanks go archers and that it's also recommended to have the overall strongest player as pocket. I get that it makes sense for the pocket player to have mobility. But why is it the meta to have both flanks go archers? Couldn't you apply faster pressure on your opposing flank with a scout build? And why is it advisable to have the strongest player in the position that is most likely getting pressured the least? I'm sure there's good (and pretty obvious) reasoning behind this, but please, try to open my eyes to it. Also, general tips for 3v3 RM are very welcome.