Re: Jimmy Olsen's Watch
It was a simple matter of who needed it more. Perry White was often in the habit of pairing up his best reporters, Clark and Lois, for starters so whenever Lois wasn't tailing Clark trying to prove he was Superman they were working together. Thus, most of the time Lois got in trouble Superman was on the scene anyway.
This wasn't the case for Jimmy. As a freelance photographer, Jimmy could be assigned to any story any where. Thus he wasn't as easy for Clark to keep an eye on as Lois was, thus Jimmy needed the signal watch more then Lois.