Why is 遞 = (辶 + (厂 + 虎))?
说文解字：更易也。从辵虒聲。

Actually, 遞=辵+虒, it's a pictophonetic character which original meaning is "to alternate".

The meaning radical(形旁) 辵 carries the basic meaning "to walk one moment and stop the next".

The sound radical(声旁) 虒 only indicates the pronunciation of 遞(dì).