[Too poor to retire]

An isolation transformer is for YOUR safety, not necessarily the radio or TV's. The last thing you want to do is accidentally touch a ground source on your bench, and a hot or live source in the unit you are working on. If you keep caution as your top priority (one hand in your pocket while taking live voltage measurements, for example; not standing in water  , things like that), one might go without an isolation transformer. 
Dan