I have no idea if this is accurate or not, but there is this general stigma from both sides that "no decent programmer worth hiring fulltime in hotter markets/companies would/should agree to a contract/temp/trial job".

I think de-facto fulltime jobs i've seen end up kind of like that - if you don't work out in X months, nobody will shed a tear about kicking you out - but this is still perceived as a more expensive operation that should be avoided by having a "proper" interview process. On which nobody can ever agree, but that's the sentiment.