Yep, let's pretend that not all maps have tons of yellow and green cover and the only thing you have to do is move 2 steps left or right. What are we talking about....?
IS sections have a lot going against them because they have to remain stationary and in cover to get their bonuses. this makes IS only effective while defending from cover and weak against anything effective against stationary targets and anything that forces them to move. it's not an issue of cover availability (which on many maps is sparse in key areas) but a matter of IS only being useful in specific situations.