why are there horizontal studs in older mobilehome walls

I own a 1969 Champion mobilehome.

I am installing new 3/4 inch wall boards to help sound resist the outer walls better than the very thin 1/8 panel boards that used to be there.

Why are there 3 rows of 1.5 inch wide horizontal studs that run across the 2.5 vertical studs? (notches cut into the verticals allow the horizontals to lay across and be flush)

I assume they are there to keep the original panel boards flat and keep them from bowing inwards over time. (in other words, gives more surface area for panel boards to lay flat against)

Since I'm nailing up solid wall board now, I assume I can take these horizontal strips away.

I just want to make sure they are not there to help keep the overall stability of the wall frame in place since the vertical studs are only 2.5 inch wide and 16 inches apart.

Any thoughts? I can't seem to find one mention of these horizontal studs in the walls and why they need to be there.

DT
Northern California