Why No Power Button on Some Phono Stages?

I am upgrading my phono stage, and several of the ones I have shortlisted do not have a power switch/on-off button.

Why is this? Is the user supposed to keep it powered up all the time, or manually unplug the power each time?

I know certain electronics are supposed to have better sound once they have reached thermal equilibrium, but that doesn't mean I want to keep it powered up 24/7.

Switching the phono stage power off from the power strip is a PIA, as it would switch all of my other components off, and I'd lose by tuner settings.

I want to choose the phono stage by sound quality, but an on/off switch is a major convenience factor for me. Why do some manufacturers leave it off?
IMO, most electronics sound better after warm up and they will last longer without the turn on surge (if heat build up is not an issue like in a preamp).

In the case of SS phono preamps the current draw is tiny so there is little reason to turn it off.
Look at it this way...
The doorbell on your front door always stays lit up, and its transformer always has current going to it. Should you be concerned?
SS is best when it is left on 24/7, the designer knows this, hence the lack of a power switch.