Doyle limps connectors, because he wants to play them against AA/KK/AK and he knows if he raises first, the AA will re raise and he can't stand the pressure. If he's raising SCs it's because he was raising air anyway.

It's important to note that his plan is to move people off hands, especially when he flops a SD. YMMV. He's not looking to call down with a draw (much).

Really, guys, read it. It's still the bible. It's worth it just for the personality alone.