I found the muzzle blast to be far worst to the sides then directly behind them.
I stood 20 feet quartering behind a .50 cal shooter once.
The shock wave is shocking.
.50 Cal’s, tannerite and bump stocks...three items that require adult supervision.
The sideways blast of the muzzle brake breaks things! Read about the tank muzzle breaks as the guns got bigger, higher muzzle velocity from the early even before and during WWII.
Turns out the sideways muzzle blast screws up the supporting troopers walking (crouching) near the tank if it is moving slowly; blows dirt and debris up around and near the tank if it is static and dug in. Or near a building or sandbags trying to be concealed. Worse, if there is no wind and the gun is fired from behind concealment, the dust cloud marks exactly where the shot came from - but blocks the view of the tankers from making the next shot quickly.
Adding the muzzle brake reduces recoil, so the turret trunnions can be lighter weight, and also allows a greater up and down range of the barrel & block because they don’t need to recoil as far. Lighter weight and greater elevation gives more range for the tank and the weapon, and are cheaper. So there are definite advantages to using a muzzle brake to the designers and program managers and generals buying the tank, but disadvantages to the troopers dug in near the tank.
Besides, the troopers getting blasted are not tankers, and the people who cannot see are not the designers and the generals, and a muzzle brake’s problems don’t matter if you are firing at speed. (Which is a cool thing for a tank.)
Guess who most often wins the design game?