Remember how bad Microsoft Office was when you transitioned to 2007? Everything moved and you couldn't find anything! Now imagine that you are used to doing everything the same way for 12 years now. It's going to take a few weeks to figure out how to do your every day tasks again. A company can train you, costing profit; or they can wait for you to figure it out yourself, costing sales.
Say a company makes 10k a year for each employee, that's 200 dollars a week. Each of their employees makes another 500 a week in their own salary which means that the employee brought 700 dollars into the company each week. Say it takes just a week for an employee to catch up and perform his duties at 100% of pre-upgrade level and during this time, he performs at only 50%.... Now the employee is bringing in 350 but taking out 500. Your upgrade, which even if it's free, is now $350. This will take nearly an entire month to break even. For what? Long term gains 6 months from now.