they have desktops designed for that purpose too, all in all i'd take one of those, that way i could build it from the ground up and have one then upgrade it later on. on the plus side if you spill bunch of stuff on the keyboard it won't break, especially if you get one of those roll up ones.
Why yes, it's far easier and more practical to lug around a monitor, keyboard, mouse, desktop case, and various wires than to take a silly laptop!
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if you have ever taken apart both a laptop and a desktop, you'll notice that they have pretty much the same stuff. keep in mind we are talking about a gaming laptop, for a gamer. so you are still talking about a mouse (no real gamer uses a touch pad), a keyboard, a monitor, and a power supply. both fit in a backpack, and both need a wall socket. the desktop has one extra wire (for the keyboard), is bulkier and has a negligible weight increase, while it is also more upgradable, cheaper, and slightly more durable. if the downsides bug you, then there are better options than a gamer laptop.
frankley a gamer laptop is a middle ground between a laptop and the current version of baby AT desktops , it can't do either well enough to replace them, and the differences between the two is entirely in power consumption and battery capacity, so unless there is some sort of energy breakthrough to make electricity from a power plant virtually free there won't be a gap wide enough to warrant a gamer laptop.
p.s. and we haven't even gotten into the minipc, or mac mini.