Owning a gTLD isn't the same as registering a trademark. It's on par with petitioning the local government to rename the street your business is on to your business name. There's an incentive to fight for your trademark, Apple would probably sue anyone starting a business with the word Apple in it if there was any chance that the company does anything with technology. However, Apple has no ownership of the word Apple. I could start a pick your own apple orchard called Apple Farms and buy the gTLD so I could have pickyourown.apple.

I agree that owning a gTLD is not the same as registering a trademark, but I'm claiming that to a company it's the same as protecting their trademark. For the same reason that companies register their names on every new social networking website, even if they don't actively use it.

To give a slightly ridiculous example (just for fun), just as someone could make pickyourown.apple they could also register tim.apple and start an excellent phishing campaign.