As someone who's had to travel by air with a baby and a very young toddler, I have to tell you that your nerves are shredded by the time you get onto the plane. Miles of walking (you can't usually get the buggy onto a moving walkway), constantly looking for specialist bathroom facilities, trying to time feeding schedules, at any one time at least one child making a loud noise - it can be hell. Then you get to the gate and they take your buggy away, and you wonder what would happen if you had to deplane in a hurry....
The thing about babies is THEY CAN'T WALK. You can't put them down for even a second unless you're willing to lie them on the ground under everyone's feet. With two babies, you have no hands free for anything. If the buggy is put in the hold, you won't get it back if they need to get you of the plane fast. You'll be standing on the tarmac with arms struggling to hold two heavy objects. This constant sense of vulnerability is...not unstressful.
In other words, FAs need to be taught to treat mothers travelling with babies as if they're grenades with the pins out. They're not normal passengers, they're people being stress-tested by psychopaths.