Yes, its good not to use pulling plug to power amps on/off.
In the mid 1980s I used a Hafler DH-500 power amp, built mine from the kit Hafler offered. These were big 500 wpc amps designed and built to a tight budget. Great value for a high power MOSFET amp. But no design budget for a turn on surge suppression circuit. With a power transformer that could double as a boat anchor and power supply caps as big as beer cans the DH-500 would often burn out its power switch due to the repeated turn-on surge. I was 'lucky' because my DH-500's power switch failed by welding its contacts together. You literally could not turn it off, push on the rocker and it would not move. So I started turning it on by plugging it in and off by pulling the plug. Like charmerci with the occasional spark down in the power strip's socket. After a few weeks of this abuse (guess I was in no hurry to replace that power switch) one day I looked at the amp's AC plug and about 1/3 of one of the blades was gone its end uneven and ragged. With each 'spark' some of the metal was vaporizing and/or getting arc welded onto the socket's contact.
A little electrical engineering trivia on this. The reason sometimes you get a spark and other times none is we are dealing with AC (Alternating Current) voltages. Sixty (or fifty in most of the world) times a second the voltage on the AC sockets goes from plus 60 (in USA or 120 elsewhere with 240 volt power) volts then to zero volts then to minus 60 (or 120) volts. When at the random moment you plug in the voltage is at or near zero volts, no spark. Next time that random moment you plug in and the voltage is near the positive or negative peak voltage there is enough energy (potential difference in engineer speak) for the voltage to jump the gap when the plug's blade gets close enough to the socket's contact. If you see a spark its the electrons jumping the gap. When you hear a 'pop' its those electrons superheating enough of the surrounding air molecules to make a tiny pressure wave we hear as the pop sound. When the power switch is open, in the 'off' position, the load is disconnected so as plug approaches socket the voltage does not 'see' the potential difference and be induced to jump the gap. Audio power amps are prone to this because as mentioned in my Hafler story they have big power supplies that can draw a lot of current as they power up. Common appliances that lack power switches like a phone charger have tiny power supply elements (and occasionally more rigorous design) that draw little current as they power up so they are not prone to such misbehaviors.
