I only have a little experience on the 737 (bout 200hrs)
But heres my guess (im not the man with the van, i jus fly em),
Our company procedures when on an autoland or landing on a slippery rwy is to use the crab technique down to touchdown up to max crosswind, which for us is 15kts on autoland and half that for slippy rwy!
My guess is that (especialy for the older planes) thru time subjected to this altho not constantly (and hey havent you ever landed and thought oops...maybe my big boot wasnt heavy enough!!! err cause i havent...honest!!
) they aint gonna stay
bang-on straight forever!!! Thats why i believe when ya taxi behind one, it looks like somebody screwed the mains on that day without their set square!!
Thats jus my idea, think prob only an eng on type could shed some true light on this one?
Tee