So she’s educating me, huh? Just like I do my Clients. 
As a plumber who has de-winterized many houses I would NOT turn on any water. I’ve had as many as about 16 splits that I had to repair in one house.
My first paid inspection was a house that had been winterized. The agent and buyer wanted to turn the water on even with my word of caution. Every valve started leaking! They did take my advice to be prepared to turn water off immediately, which they did. 
This brings up a good piece of advice (regarding plumbing) I give all my clients…
If you ever perform plumbing repairs (installing sink faucets, washing machines, general plumbing leaks) or ever need to turn off the water supply in general… ALWAYS use the municipal water valve (usually at the street level)…
The difference in responsibility for repairs is huge!
I Tell My Client It Is The Responsibilty Of The Realtor To Ensure Utilities Are On , And That No Hi Insurance Will Cover Us In The Event Of A Busted Pipe. Like Will In Hialeah , I Have Been Inspecting Nothing But Empty Homes Lately. Some Realtors Get It And Some Dont.on My Summary Page At The Top Is A Section For Systems That Were Inoperable (broken) Or Didn’t Have Service(water,gas,electric) To Them. Always Talk To The Client First To Convey Or Cya Over Responsibilty Over The Utilities.
What if there is no Realtor.
And provided that there is, and the systems still are not turned on despite your warning, what do you do about it? Do you charge the Realtor a return visit fee? And if so, how do you get them to pay?
I let my client know while setting the appointment that it is their responsibility to make sure the utilities are on and pilot lights are lit, etc. (Mostly this is for bank repos and the like.) I let them know that everything needs to be on to get the full benefit of the inspection.
I let them know that I will be glad to inspect the home in the condition I find it and that I charge $100/hr to come back later if the utilities aren’t on. (I’ve made some changes to this depending on the situation but they know what can happen up front.)
I suggest that they may want to work with their realtor to make sure everything is on and, typically, they turn it (getting utilities on) over to their realtor but my agreement is with my client for return trips.
They like my concern that they get the best benefit of a full inspection and usually call back to reschedule when they know the utilities are on.
I do exactly like you, Larry. But I also advise them to get a confirmation from the listing agent (preferably by email) that all utilities are on and that all areas are accessible. That means they can charge the listing agent if they screw up.