What caused Spider-Man to get a reboot? why is the franchise getting rebooted? it really sucks, how come?

I've known about this for a few months now, and I'm sure everybody else already knows that it was announced at the beginning of the year that Sam Raimi and Tobey Maguire will not be returning, the next Spider-Man. Marc Webb(who directed 500 days of Summer) will be the director of the Spider-Man reboot, seriously, why is Spider-Man getting a reboot? The previous 3 films were not beyond horrible like the Hulk movie from 2003 directed by Ang Lee and Batman and Robin from 1997, the one with George Clooney. Seriously, all 3 of the Spider-Man movies directed by Sam Rami were huge box-office hits, so why the reboot? Overall, I'm completely against the reboot, so why?