Public and companies with government contracts are different than the private sector, and selling taxpayers on a conference in Las Vegas can be difficult.
In the private sector, companies should budget about 5% of annual salary for training. That includes time and expenses. Usually our approach is to make sure the employee has some skin in the game-- either pay part of the cost or take PTO to attend if it isn't after-hours.
As an employer, I am generally torn on the matter though; much of the benefit is to the employee rather than the employer; I care that you can do your job not that you have a piece of paper that says you can do your job. New technologies, keeping skills sharp, networking... all of those things have a split benefit.