In other words, why do physics departments demand one or more post-doc stints (lasting as much as 5 or six years) for their faculty applicants, when many engineering departments recruit fresh PhDs? Ponderer ponders this and related questions:
The whole situation is not fair. Assuming an average college grad is 21 or 22 years old, going into experimental physics means you are likely to graduate by the time you are 28 (give or take). A 3-year postdoc means you are 31. Two postdocs (that are not uncommon in physics nowadays) stretches starting age to 34 or so.
In comparison, engineering PhD may start her or his faculty career at a tender age of 26 or 27, barely out of the diapers as far as I am concerned. It obviously depends on the field, but there are personal blog accounts in the blogosphere of getting faculty offers from ivy league schools during their 5th year of grad school, before defending PhD thesis.
This is a serious problem for a number of reasons ...