Because they are expensive
Total rubbish, if you think hiring a professional is expensive try hiring an amateur!!
Next time you see a day rate you think is too high, phone your plumber and ask what he charges.
I reapply for my contract every 3 months, when did you last reapply for your job ?
Finally if you don’t like contractors then just refuse to work with them, your company will appreciate your honesty and flexibility.
I am sick of people playing down the skills of contractors, if your employer thought YOU could do he wouldn’t need us.