In the episode "Hollow Pursuits", Barclay built really creative and fun holodeck fantasies. Why did he join Starfleet and be burdened with huge responsibilities and stress when he can simply be a loafer in the Star Trek world and play on the holodeck all day long to feed his wildest fantasies?
In the Star Trek world, nobody works for a living. A Vulcan would conclude, after watching kids and even many adults today, that most humans' preference is to play the holodeck all day long and not answer to a demanding boss at work. Someone like Barclay would surely be addicted to the holodeck.