Those folks have found a way that is easy for them 
Just kidding… but seriously… it gets easier with time.
If you think back to when you first learned chords, it probably seemed pretty hard to get the correct notes to all ring clearly (and none of the incorrect ones). Your body figures it out over time. A few tips that come to mind: 1) Many people have better success with their barre finger not perpendicular to the fretboard, with the knuckles pointed slightly toward the headstock. 2) If you rely solely on clamping pressure with the thumb, it is hard to generate much pressure. Try to use the weight of the arm to pull into the fretboard, that way you don’t need much clamping pressure. This is hard to describe, but easy to feel when you get it. 3) Realize that most barres (all except for a weird one) don’t require fretting all 6 strings. Look at what notes need to be fretted. Make tiny adjustments to prioritize fretting those particular notes. It could be that a string is landing right under a knuckle. 4) (The anti-barre advice) Learn some alternates like the F shape with the thumb wrapped for the root on the low E string. I use that shape all the time and can get into it and out of it easily and quickly.