Why compile to bytecode

Kevin, Donal, and Miguel write eloquently in a clt thread [L1 ].

[DKF: Someone care to go through that thread and extract the best/most-relevant bits? I'd rather us not rely too much on Google's largesse; Tcl is independent of them.]
PYK totally agrees about not relying on google groups comp.lang.tcl archive, and has some tentative plans to address this issue for the wiki. The great Google Groups URL switcheroo a few years ago wreaked havoc, and there's almost no way to even search for information about that event.