Hello. Why everyone on videos and images put their espresso cups on top of the espresso machine?
Sorry i'm new to home barista hobby.

Mostly to keep them warm. Many espresso machines use the heat from the boiler to keep the cups warm. It is also a convenient place to store the cups.

Currently owning a Lelit pl41 Plust , can i do it with my espresso machine? So i put the cups on top and when i'm starting my machine , till it's ready for the extraction , the cups should've been warmed up right and be ready for use ?

I don't know that machine but probably. It's important to have the cups nice and warm so they don't suck the heat out of the espresso when it's poured. Once you wash the cups, just put them back on top of the machine and leave them there overnight until you make another espresso.

I've never done that with any machine as I don't need a very warm cup and won't take the chance of causing unnecessary scratches. I've also seen cases where the user put wet cups back on the top leading to moisture making its way into the electrical side of things.

Reclaim lost counter space.

I'd never put it wet on the espresso machine , could cause electric problems. So i'll just let them on top of the machine to see how warm they get , otherwise i'll extract hot water from the machine into the cup and see the taste difference.

JohnB. wrote:Some of us like to leave the cups at room temp so that they do draw down the shot temp quicker. Even with a room temp cup it will still be a minute or two before the shot is cool enough to drink.

True. I found a distinct improvement when I stopped pulling shots into very hot cups that had been sitting on the cup tray for long periods of time. But I also found that the espresso cools off faster than I want when I use cups at "room temperature". So I put my cups on top of the machine when I start the session to take off any chill (common in the winter in my house.) By the time I pull the first shot (always straight espresso), the small cup is only slightly warm. By the time I pull the second shot (always a cappuccino), the larger cup is slightly warm.

JohnB. wrote:Some of us like to leave the cups at room temp so that they do draw down the shot temp quicker. Even with a room temp cup it will still be a minute or two before the shot is cool enough to drink.

Try keeping a cup in the freezer and pulling a shot into that. With the right coffee it's really nice.

I mostly use room temp cups and never understood the heated cup thing. They say heat hides all kinds of defects and that's likely why the masses like their starbucks, DD, and the rest to be super hot.