It's not good for the plugs itself though, I often get this spark with mine when I plug it in and the prongs are rather scorched
I know those switches aren't always available, in Europe they're also very uncommon, it's just UK/Ireland that do have them. An extension cord with a switch might help in that case.
By the way the reason it does this is because it's rapidly filling up its capacitors when plugged in, they're a bit like very low capacity batteries that charge/discharge very quickly. It uses those to compensate for small power interruptions and remove ripples.
The high current and thus arcing when plugging in is called 'inrush current' and is common for switched-mode power supplies. It's also dependent on the state of the sine wave at the precise moment when it's plugged in - as it's alternate current it could be anywhere on the sine wave at that moment. If the sine wave is near the middle (near zero volts) there is no such spark and the slow buildup of the voltage will charge the capacitors more gently. But if the sine wave happens to be near the top (for 110V it will be even higher than that, as 110V is the average, not the peak voltage), it will cause that inrush.
That's why components such as electrical relays often have 'zero detection', which means they'll wait to switch on until the sine wave goes through zero again, which it does 120 times a second (for 60 Hz). But Power Supplies don't usually have this, it's not practical because those electrical relays also need power themselves.
Anyway maybe it's a bit off topic but I just wanted to share that background and information as to why it happens only some of the time.
