The practice you suggest would not be the result of the monopoly status of the utility. That would be the fault of the PUC for allowing such a shady practice to exist, and PUC's typically have a very heavy citizen (i.e., tax payer, rate payer) input. If I was invested in a public utility (or any other type of industry, for that matter), I would vote to dump any board of directors that weren't "greedy". I want the BOD "greedy", profit is the business of business.
--Boot Hill
I agree with you, to a point. However, in a monopoly situation, the rules are different. For capitalism to be a "good thing", there must either be competition or regulation to temper the ambitions of any one company. Particularly in the utility business, which is by definition selling basic needs to customers, the profit motive should be held in tight control.
There are plenty of industries in which to make a healthy profit. I think there are also those which, by their nature as monopolies coupled with the high importance of their product to the basic needs of their customers, should be regulated to a modest profit. If an investor wants to make a killing, it shouldn't be in a utility company, IMO.