Why No Power Button on Some Phono Stages?

What Al said.
I nearly never turn off the solid state components in my audio system. The OP did not say whether the phono stages he is considering are solid state or tube type (or maybe it came out in subsequent discussion which I have not read). The AV receiver in my home theater system has never been shut down since new (about 6 years).

However, most of my gear is tube type, and I do shut down all that stuff between listening sessions, even though I know that turn-on places certain stresses on tubes and the components that feed them.

Dear Czarivey, I don't want to frighten you, but if you are really concerned about destructive power surges due to lightning, you should not only turn off but unplug as well. (You do not say what is the source of the "devastating surges".) A lightning bolt does not respect a power switch.

Dover, I share Czarivey's dismay. What do you mean by "behavioural memory" of a power supply capacitor, or was that just an attempt at humor? If the latter, it worked.

Because most know they sound better when on all the time, too small to cause a fire and the extra 1$ a year it costs ain't gonna break anyone or hurt the North Pole.
IMHO though, anyone who goes away and leaves tube gear on is a fool.

Definitely, Lewm, I forgot to mention that it's being unplugged from the wall.The sources are various: unstable main transformer, winds and devastating lightning bolts.

Lewm -
Memory distortion in audio components, ie resistors and capacitors, is recognised by many now. A common example that some people may be aware of is batteries. If you keep recharging a battery before it is discharged fully, it can form a "memory" whereupon it wont work any more when it reaches that point that you kept recharging it, whereas if you completely run the battery down before recharging, then it will work at all levels.
I run tube preamps where the operating voltages are quite conservative and therefore can be left on all the time.
What I am saying is that if I dont discharge the power supply completely from time to time then those power supply electrolytics will form a memory ( similar to the battery example ) as they have never been fully discharged, or even overcharged on turn on.
Another way of thinking about this cycling, is degaussing your cartridge.
And the answer is yes, I hear a freshening up of the sound when I turn off the components for a day or so.