Small, portable devices require less valuable space in the marking truck and speeds up the processes of loading and unloading it for measurement, with the added benefit of being easier to move from one site to another. On air travel, it can be transported as carry-on luggage, avoiding extra charges.
Knowing that you can move your equipment in a backpack – even by airplane without extra fees or battery warnings – with little additional effort is extremely advantageous.
Finally, portability has solved an old problem: operators fatigue by muscular effort.
If you still carry a 10-kg device to work with, you are far behind.