I don’t see the need, but I do know that many do this. Generally it’s not to lower braking force, as the vast majority of boat trailers with brakes have surge brake systems. Usually, this is to prevent lighting issues. Wired correctly this is not necessary. With trailer frame grounded systems, that may be helpful. After getting tired of chasing issues and replacing lights, I retired the whole trailer.
All lights have power and ground wires. All trailer wiring is tinned marine grade wire. The submerged connections are heat shrinked, and covered with liquid electrical tape. Each wire (power and ground) goes from the light to a junction box at the front well away from the water.. 7 pin trailer plug and EOH system is also connected to the junction box. I launch exclusively in salt water, and this system has been quite trouble free for many years.
