Why did no one on the force use the Chrono Morphers before?
 

They were just lying around in some suitcase. Why? Why did Alex have one?

Re: Why did no one on the force use the Chrono Morphers before?
 

Since the morphers are DNA encoded, I think they didn't just want to give it to anybody. Watching the first ep, Alex is considered the best of the best among the officers so him deserving one seems like a no brainer.

Re: Why did no one on the force use the Chrono Morphers before?
 

Perhaps the powers were knew and weren't active yet. Alex was just the first Ranger to be activated. Its quite possible that Jen's team were already in the running to become Rangers.

Re: Why did no one on the force use the Chrono Morphers before?
 

that's a good possibility and it's also possible that the other 4 weren't needed since Alex had everything under control all on his own. Why activate additional powers if you don't need to?