Until relatively recently with the move to "instant-on" and "standby" modes to enable faster start-up all gear was fully powered down when the switch was turned off. Most gear with clocks and settings memory has internal battery power to retain the time and settings so disconnecting mains power should not be an issue. Well designed gear should not be hurt by daily a powering up/down. Powering full up can help electrolytic caps remain properly formed.
The biggest issue is likely the chance of power surges (e.g., lightning strikes and switching transients) finding their way into your gear. Leaving gear turned on in standby mode does use some power.
So if you live where there is power instability and/or a lot of lightning and you are not fully isolated by a quality UPS disconnecting from the mains may buy a bit of additional protection.
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